16urn:lsid:arphahub.com:pub:C15B38C9-9A3E-543C-A703-DD742F25B4D5Advanced BooksABPensoft Publishers10.3897/ab.e178106178106MonographPalaeobotanyBulgariaThe Postglacial Vegetation History in Southwestern BulgariaA Paleoecological Approach. Second updated and revised edition.TonkovSpassimirstonkov@abv.bg1Sofia University "St. Kliment Ohridski", Sofia, BulgariaSofia University "St. Kliment Ohridski"SofiaBulgaria
20261106202615C9CDFDF-780D-5D0C-B6BE-7179B2DD2635Spassimir TonkovThis is an open access book distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Preface to the second edition
The updated and revised edition of this book presents and discusses the results from the palynological and paleoecological studies conducted in Southwestern Bulgaria with my participation over the period 1985-2025. This montane area rich in numerous lakes, peat bogs and mires is located in the central part of the Balkan peninsula and has always played an important role in unravelling the Late Quaternary vegetation history in Bulgaria. The modern development and achievements of the research methods applied (pollen analysis, plant macrofossil determination, radiocarbon dating, sediment and geomorphological analyses, charcoal analysis, archaeobotanical research, computer software, etc.) allowed to evaluate and synthesize in details the available paleoecological information on the vegetation development in this part of the country for the last 30000 years. It was also important to demonstrate the millennial role of humans in the transformation of the natural environment after the establishment of agriculture and the practice of stockbreeding.
The content follows the structure of the first edition published in 2021. Two new chapters are included related to the vegetation history in the Western Rhodopes and Vitosha mountains. Of particular interest and importance is the long pollen core from Mire Kupena in the Western Rhodopes Mountain which extends back to the Middle Pleniglacial. The results from the investigation of several new sites in the Rila Mountain are also included in the relevant chapter. In addition, where appropriate new pollen and plant macrofossil diagrams, figures, tables, photos and references were added. The final chapter is a summary about the overall picture and the specifics of the postglacial vegetation history in the study area.
In the course of the preparation of this edition several outstanding scientists who had a major influence on my scientific career passed away, namely Prof. Elissaveta Bozilova, Prof. Hans-Jürgen Beug, Prof. Göran Possnert and Prof. Angel Velchev. I would like to dedicate this book to their memory, and also to the members of my family for their unreserved support and encouragement.
It is a pleasure to extend my gratitude to the Director of the Pensoft Publishers Prof. Ljubomir Penev for his interest in paleoecology, the financial support, and all the facilities provided by his staff to prepare the book for publication. I am thankful to Vasil Peev for the preprint and graphical design.
I will be glad if this edition attracts the interest of scientists working in the fields of Quaternary pollen analysis and vegetation history, paleoecology, paleoclimatology, paleogeography, landscape ecology, forestry and archaeology.
Sofia, April 2026 Prof. Spassimir Tonkov, PhD, DSc
Preface to the first edition
This book presents the results from the palynological and paleoecological studies conducted with my participation in Southwestern Bulgaria during the period 1985-2020. The study area has always played a key role in the investigation of the Late Quaternary vegetation history in Bulgaria since the middle of the past century. With the development of the research methods (pollen analysis, determination of plant macrofossils, radiocarbon dating, sediment analysis, computer software, etc.) in the last decades it turned out to be a challenge for me to evaluate critically again and synthesize the paleoecological information. In my opinion, such approach allows to reveal in more details the general trends of the postglacial vegetation development for the last 18000-15000 years, and to take also into account the role of humans in transforming the natural environment after the establishment of agriculture and the practice of stockbreeding in this part of the country along the Struma river.
The content is organized in several chapters starting with introductory notes on the scientific importance and the main purpose of research in the study area, a brief assessment of previous investigations, and a short review of the research techniques applied. The subsequent chapters present the original paleoecological data and the vegetation reconstruction for each montane area in uniform way, starting with the high mountains Rila and Pirin, the Konyavska and the lower west border Osogovo, Maleshevska, Vlahina and Belasitsa mountains. Then follows a summary of the human occupation and the millennial anthropogenic impact on the vegetation cover and the environment since the Neolithic epoch. The final chapter presents to the audience the main conclusions and specifics of the postglacial vegetation history in Southwestern Bulgaria.
It is my pleasure to dedicate this book to my teacher in the fascinating world of palynology Prof. Elissaveta Bozilova and also to the members of my family for their support and encouragement during all these years of academic research and teaching in the Department of Botany at Sofia University St. Kliment Ohridski.
I extend my gratitude to the Director of the Pensoft Publishers Prof. Ljubomir Penev who kindly provided all facilities including financial support. I am also obliged to Teodor Georgiev who was responsible for the preprint and the graphical design.
I will be grateful to all colleagues who are interested in this research topic and share their critical remarks and comments.
Sofia, May 2021 Prof. Spassimir Tonkov, PhD, DSc
1. Introduction
The development of the natural ecosystems is a reflection of global climate changes since the termination of the last glaciation. For paleobotanists and paleoecologists the history of vegetation during the Quaternary, when cold and warm intervals of different duration and amplitude alternated, the changes in the environment are result of the complex interaction of various factors, the most important of which is climate. The concept that vegetation is in equilibrium with climate for a certain period of the Earth‘s history has been confirmed in different aspects with the application of modern research methods. The dynamic equilibrium has been affected by longer or shorter climatic oscillations in response to changes in orbital factors, as well as the hydrosphere-atmosphere interaction, the formation and disintegration of the continental ice sheets and mountain glaciers.
The use of indicator plants, modern analogues of paleovegetation communities and dynamic computer models, allows to reconstruct the paleoclimate and paleoecological conditions for certain periods of time, as well as to predict the future trends in global changes facing the human society. In this process is necessary to take also into account the increasing role of the anthropopressure, which over time acquires significant proportions in the exploitation of the environmental resources.
The integrated paleoecological research approach provides data on the history, distribution, ecology and relationships between plant species and their response to climate and anthropogenic changes. In the study of the past vegetation the main role is assigned to the paleobotanical methods of investigation among which pollen analysis and the determination of plant macrofossils are most frequently used. Pollen grains and spores are the most abundant microfossils providing direct information on the past flora and vegetation, and plant macrofossils of local presence as they can often be identified at species level. The sequence of the changes established is confirmed by the application of local or regional chronologies, and in the last decades by the study of ice cores from Greenland, Antarctica and other parts of the world.
Arising from the last glaciation, significant changes have occurred in the flora and vegetation - appearance or disappearance of certain plant taxa, transformations in the composition and structure of the plant communities, and in the habitats of a number of species. For Southeast Europe, the Balkan peninsula in particular, the nature of these dynamic changes is rather diverse and complex taking into account the interplay of abiotic and biotic factors. Also, within this peninsula a variety of modern vegetation types exists with different postglacial history.
There is a significant amount of paleobotanical and paleoecological evidence collected for certain regions of Bulgaria regarding the postglacial development of the environment and vegetation in response to climate changes, and, in recent millennia to human activities. The territory of Southwestern Bulgaria is one of these regions that serves as a linkage between the northern parts of the Balkan peninsula with continental climate and the southern areas, where the mediterranean climate influence is clearly manifested. This territory comprises a mosaic of high and low mountains, valleys and rivers, an area that was inhabited already in the Early Neolithic about 8000 years ago. The highest mountains Rila and Pirin were glaciated during the Quaternary and the neighboring areas were affected by the periglacial climate.
Traditionally, in this part of the country the most numerous paleobotanical and paleoecological investigations on the Late Quaternary history of flora and vegetation are conducted and each subsequent step represents a new direction in this research.
In Southwestern Bulgaria suitable sites for paleoecological studies such as lakes and peat bogs are located in the Rila, Pirin and Western Rhodopes mountains, and also peat bogs and mires in the lower mountains. These wetlands are product of the natural environment and their complex investigation results in acquiring of important information on the historical identification and evolution of the modern ecosystems with their biodiversity. The sediments accumulated in the lakes after the retreat of the mountain glaciers provide very good opportunities for paleobotanical, paleoecological and paleogeographical reconstructions. Lake and peat sediments develop in a certain sequence and constitute a specific archive of biotic and abiotic changes in time and space. The climate signal from the sediments is mainly a result of complex interactions in the environment, manifested as variations in the autochthonous organic components, mineral components and micro- and macrofossils of plant and animal origin.
Paleobotanical and paleoecological studies on the Late Quaternary vegetation history in Bulgaria started in the first half of the 20-th century and to this day they are most numerous in Southwestern Bulgaria. The palynological pioneer studies of peat bogs in the Vitosha Mountain are well known (Stojanov, Georgiev, 1934). Sediment cores from eleven peat bogs located in the spruce forest belt and above the tree-line were analyzed. The pollen percentages of the main forest constituents (Picea, Abies, Pinus and Fagus) were presented with separate pollen curves while those of Salix, Quercus, Corylus, Betula and Tilia considered as secondary elements were shown by a cumulative pollen curve. It was concluded that peat accumulation has started in the Subatlantic when beech replaced part of the conifers. In the following decades these investigations were expanded and a number of pollen diagrams from sites located between 1400 and 2200 m were published which revealed the alternation of several forest phases but without sufficient and reliable chronological control (Petrov, 1956; Filipovitch, 1988).
Later on, palynological studies of peat bogs and former lakes were initiated in the Rila and the Northern Pirin mountains. These investigations marked a qualitative leap with the application of radiocarbon dating. As a first step the palynological research in the Rila Mountain was focused on peat bogs located in different parts of the massif, most of which were formed during the Late Holocene (Subboreal and Subatlantic). The age of the sediment cores and the succession of the forest plant communities were determined by a limited number of radiocarbon dates (Bozilova, 1972, 1975, 1976, 1977, 1981). Lateglacial sediments from two sites in the northwestern and southwestern parts of the mountain were studied but without a detailed chrono- and biostratigraphical division (Bozilova, Smit, 1979; Bozilova, 1981, 1986). It was proposed that a number of deciduous and coniferous tree species survived the harsh glacial conditions at lower altitudes in local refugia at 800-1000 m, where suitable microclimatic conditions existed, with their subsequent vertical migration in the Holocene (Bozilova, Tonkov, 1983, 1985, 1985a; Bozilova, 1986; Tonkov, Bozilova, 1988). The fluctuations of the upper timber-line were also discussed in the view of climate, ecological and anthropogenic changes (Bozilova, 1975a, 1995).
The results of the palynological and paleoecological studies in the Pirin Mountain showed many common features with the Rila Mountain in terms of vegetation dynamics and climate changes in postglacial time but also some site-specific features constrained to the more southern location. Peat bogs in the northern part of the mountain were investigated and it was established that most of them originated since mid-Atlantic until the beginning of the Subatlantic (Bozilova, 1975b, 1977a; Stefanova, Bozilova, 1992; Stefanova, Oeggl, 1993; Stefanova, 1997). The results revealed the main characteristics of the plant paleosuccession in the last 7000 years. A further progress was achieved with the complex investigation of lateglacial and Holocene sediments from glacial lakes by the application of pollen analysis, plant macrofossil determination and radiocarbon dating (Stefanova, Bozilova, 1995; Blyakharchuk et al., 2001; Tonkov et al., 2002; Stefanova, Ammann, 2003; Atanassova, Stefanova, 2003, 2005; Stefanova et al., 2003, 2006, 2006a; Bozilova et al., 2004).
The age of the majority of paleoecological sites located in the vast Western Rhodopes Mountain extends back either to the last 7200 years (Panovska, Bozilova, 1994; Bozilova et al., 2000) or to Subatlantic time (Lazarova, 2003; Lazarova, Filipovitch, 2004). Moreover, the radiocarbon control of several sites is lacking or insufficient and the time resolution of the upper parts of the relevant pollen diagrams is rather low. The two exceptions are Mire Kupena (Bozilova et al., 1989; Huttunen et al., 1992; Tonkov et al., 2014) and the peatland Shiroka Polyana (Filipovitch, Lazarova, 2001, 2003; Stefanova et al., 2006) in which the accumulation of sediments started in the Middle Pleniglacial and in the Lateglacial, respectively.
Palynological data supported by radiocarbon dates were obtained from the investigation of peatlands in the western lower mountains Konyavska (Tonkov, 1988; Tonkov, Bozilova, 1992), Osogovo (Tonkov, 1994, 2003a), Maleshevska (Tonkov, Bozilova, 1992a), Vlahina (Tonkov, 1992) and Belasitsa (Panovska et al., 1990; Tonkov, Possnert, 2014).
The paleoecological reconstructions from Southwestern Bulgaria based on the information from pollen analyses of lakes and peat bogs, plant macrofossils, archaeobotanical finds and radiocarbon dating were used for inferring the human impact on the vegetation and landscape over the last 8000 years (Marinova et al., 2012).
The first summary of the vegetation and environmental changes in Bulgaria in postglacial time comprises also information from sites in the montane area of Southwestern Bulgaria. It was published as a separate chapter (Bozilova et al., 1996) within the activities of IGCP Project 158B Palaeohydrological Changes in the Temperate Zone in the Last 15000 Years: Lake and Mire Environments.
The possibilities offered by the complex study of sediments from lakes, peat bogs and mires in Southwestern Bulgaria remain still not completely utilized. There are issues to be resolved about the specifics, chronology and the stages of the plant paleosuccession in postglacial time, as well as the regional manifestation of the climate fluctuations. There is discussion related to the localization of glacial/lateglacial refugia of the main tree species, their rates and routes of migration in response to the rapid amelioration of the climate at the beginning of the Holocene. The information on the sedimentation processes in the glacial lakes as a reflection of the paleoecological situation after the retreat of the glaciers remains still insufficient. From archaeobotanical point of view of particular interest is the early appearance of praehistorical settlements in these lands and the millennial exploitation of the plant and animal resources by humans.
This book attempts to summarize the results from the latest developments and trends in the palynological and paleoecological studies of the Late Quaternary vegetation history conducted in the montane area of Southwestern Bulgaria.
2. METHODOLOGY
In this updated and revised edition of the book the paleoecological results of 41 cores from 35 sites (14 lakes, 17 peat bogs, 4 mires, marshes and swamps) located in the following mountains of Southwestern Bulgaria are presented and discussed (Figs 1, 2 and 3).
8AF8D19A-856D-5853-BD29-C0C2DC6E064E
Map of Bulgaria on the Balkan peninsula with the study area.
Location of sites studied in Southwestern Bulgaria.
https://binary.pensoft.net/fig/1672845
Rila Mountain: Northwestern Rila Mountain - Lake Trilistnika (site 1), Lake Ribno (site 2), Lake Sedmo Rilsko (site 3), Lake Skakavitsa (site 4) and Lake Panichishte (site 5, two cores); Central Rila Mountain - Lake Manastirsko 2 (site 6), Peat bog Vodniza (site 7), Lake Ostrezko 2 (site 8), Lake Ostrezko 3 (site 9), Lake Malko Smradlivo (site 10), Lake Suho Ezero-RM (site 11); Southwestern Rila Mountain - Lake Suho Ezero (site 12, two cores), Peat bog Vapsko 1 (site 13), Peat bog Vapsko 2 (site 14) and Lake Vapsko 2 (site 15)
Pirin Mountain: Northern Pirin Mountain - Lake Ribno Banderishko (site 16), Lake Muratovo (site 17, two cores), Peat bog Mozgovitsa (site 18); Southern Pirin Mountain - Peat bog Mutorog (site 19) and Peat bog Popovi Livadi (site 20)
Western Rhodopes Mountain: Mire Kupena (site 21, three cores), Peat bog Beliya Kanton (site 22, two cores) and Lake Blatisto (site 23)
Vitosha Mountain: Peat bog Kapaklivets-Platoto (site 24), Peat bog Konyarnika (site 25) and Peat bog Kumata 1 (site 26)
Konyavska Mountain: Tschokljovo Marsh (site 27, two cores)
Osogovo Mountain: Peat bog Osogovo 1 (site 28), Peat bog Osogovo 2 (site 29) and Peat bog Begbunar (site 30)
Maleshevska Mountain: Peat bog (site 31)
Vlahina Mountain: Peat bog Kadiytsa (site 32) and Swamp Obel (site 33)
Belasitsa Mountain: Mire Gjola (site 34) and Peat bog Belasitsa 1 (site 35)
The sediment cores were recovered with hand-operated equipments (Dachnowsky, Livingstone, Hiller, Wardenaar) and motor Streif sampler, with different length of the chambers (0.2 m, 0.5 m and 1 m), and stored in plastic tubes in refrigirator.
Pollen analysis was performed on each core at intervals of 5-10 cm and less often every 2-2.5 cm dependent on the composition of the sediments, the time for their deposition, and the purpose of the relevant study. The standard acetolysis procedure for the sample preparation was applied (Faegri, Iversen, 1989) and siliceous particles were also removed (Birks, Birks, 1980). The counting of the pollen grains was performed with microscopes Amplival, Leitz and Nikon at magnification 400-800× (1000×). The determination of the fossil pollen grains and spores was done to the lowest possible taxonomic level with the help of the reference collection in the Laboratory of Palynology, Department of Botany at Sofia University, the pollen keys and microphotographs in Beug (1961, 2004), Moore, Webb (1978), Moore et al. (1991), Faegri, Iversen (1989), Punt et al. eds. (1976-2003) and other literature sources. The pollen sum of c. 500 grains used for percentage calculations includes tree and herb pollen, excluding spores of mosses, pteridophytes, pollen of Cyperaceae and aquatics. Percentage pollen diagrams with the most common/important pollen taxa present with values >0.5% and depth/age models are constructed with the computer program Tilia (Grimm, 1991-2020). The subdivision of the pollen diagrams into local pollen assemblage zones (LPAZs) which reflect successive changes in vegetation development was facilitated by the application of CONISS (Grimm, 1987). The definition of a local pollen zone includes a letter code, a brief description of the fossil composition, transitions to neighbouring zones, and where possible, its chronostratigraphic boundaries (Faegri, Iversen, 1989). For several cores pollen accumulation rates (PAR; pollen grains cm-2 yr-1) of the main tree/shrub and herb pollen taxa are also calculated by addition of Lycopodium tablets per sample of constant volume (1 or 2 cm3) before preparation (Stockmarr, 1971). The PAR value of a given taxon is directly dependent on its abundance in the surroundings of the study site and independent of values of other taxa (Davis et al., 1973; Giesecke, Fontana, 2008; Seppa et al., 2009, etc.).
Fossil stomata from needles of conifers were identified and counted together with pollen grains in the sediments of Lake Ribno, Lake Manastirsko 2, Peat bog Vodniza, Peat bog Vapsko 2 and Lake Vapsko 2. Their presence is indicated in absolute numbers or by a symbol on the relevant pollen diagram and provides a valuable proxy for local presence (Ammann et al., 2014). The taxonomic identification was done following MacDonald (2001), Sweeney (2004), Magyari et al. (2012), Finsinger, Tinner (2020) and reference slides, particularly in attempt to distinguish stomata originating from Pinusmugo/sylvestris and Pinuspeuce.
In sediments of Quaternary age, the plant macroremains preserved (fruits, seeds, leaves, wood, fragments of vegetative and reproductive organs, etc.) provide important information for the reconstruction of the local vegetation in a given area, as they are often identified at species level and supplement the information from pollen analysis (Wasylikova, 1986; Birks, Birks, 1980, 2000). Plant macrofossils were determined from Lake Panichishte-2, Lake Ostrezko 2, Lake Ostrezko 3, Lake Suho Ezero-2, Peat bog Mozgovitsa, Peat bog Popovi Livadi, Peat bog Beliya Kanton BK-2C, Lake Blatisto, Tschokljovo Marsh-1 and Peat bog Begbunar. Additionally, for the purpose of radiocarbon dating, plant macrofossils from Lake Sedmo Rilsko, Peat bog Vapsko 2, Lake Ribno Banderishko, Mire Kupena-2, Peat bog Beliya Kanton-2C and Peat bog Begbunar were used. The samples for macrofossil analysis were separated at every 10, 15, 20 or 25 cm depending on the amount of material available. The plant macrofossils were analyzed with a stereomicroscope at a magnification of 10-80× and the wood sections were examined with a light microscope. The identification was performed with the use of atlases, identification keys, literature sources and reference material (Beijerinck, 1947; Katz et al., 1977; Schoch et al., 1988; Schweingruber, 1990; Tobolski, 2000, etc.). Cuticular analysis was also applied in attempt to distinguish the needles originating from Pinusmugo and Pinussylvestris (Struzkova, 2002). The results are presented graphically in the form of macrofossil diagrams constructed with the program Tilia (Grimm, 1991-2020). The absolute number of plant macrofossils identified from a given taxon in each sample is indicated. The presence of fragments of wood and remnants of vegetative parts (stems, leaves, etc.) is shown by an appropriate symbol. The macrofossil diagrams are divided into local macrofossil assemlage zones (LMAZs) defined by a special letter code and a brief description of the fossil composition analogous to the LPAZs.
Radiocarbon dating as an essential element of any modern paleobotanical and paleoecological study provides the basis for accurate chronological control over the tracking of changes in flora and vegetation, climate, hydrological regime, etc., archived in the sediments of lakes, peat bogs, mires, paleosoils, paleoethnobotanical materials (Walker, 2005).
In this large-scale investgation the radiocarbon dating of 178 samples was performed by conventional and AMS methods in 19 laboratories in Europe in the frame of international cooperation and mutual agreements as follows:
77 samples in the Radiocarbon Laboratory (Ua) at the University of Uppsala, Uppsala, Sweden
34 samples in the Radiocarbon Laboratory (LuS) at the University of Lund, Lund, Sweden
10 samples in the Radiocarbon Laboratory (Hela) at the University of Helsinki, Helsinki, Finland
10 samples in the Radiocarbon Laboratory at Alfred Wegener Institute (AWI), Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
9 samples in the Isotoptech Zrt. (DeA), Debrečen, Hungary
8 samples in the 14C and 3H Laboratory (Hv) in Niedersachsisches Landesamt fur Bodenforschung, Hannover, Germany
6 samples in the Centre for Isotope Research at the University of Groningem (GrN), Groningen, The Netherlands
4 samples in the Radiocarbon Laboratory (B) at the University of Bern, Bern, Switzerland
4 samples in the Radiocarbon Laboratory (RICH) at the Royal Institute of Cultural Heritage, Brussels, Belgium
3 samples in the Robert van der Graaff Laboratory (UtC) at the University of Utrecht, Utrecht, The Netherlands
3 samples in the 14CHRONO Centre (UBA) at Queen’s University of Belfast, Belfast, Northern Ireland
3 samples in the Poznan Radiocarbon Laboratory (Poz), Poznan, Poland
2 samples in the Radiocarbon Laboratoriy (KL) of the Institut fur Rheine und Angewandte Kerphysik der Universitat Kiel, Kiel, Germany
2 samples in the Radiocarbon Laboratory at INRNE, Sofia, Bulgaria
2 samples in the Radiocarbon Laboratory (Tln), Tallinn University of Technology, Tallin, Estonia
1 sample in the Radiocarbon Laboratoriy (J) of Max-Planck-Institut fur Biogeochemie, Jena, Germany
The results are presented in tables and on the pollen/plant macrofossil diagrams in 14С yrs. ВР (0 yrs. BP = year 1950). All radiocarbon dates have been calibrated to calendar years (±2σ range) with the computer program OxCal 4.3 (Bronk Ramsey, 2009) using the relevant atmospheric data (Reimer et al., 2013). The mid-point calibration value is also indicated. In this case the calibrated dates (cal. yrs. BP or cal. BC/AD) can also be considered as calendar years. It is recommended to use calibrated years in the scientific literature (Walker, 2005) which is applied in the text. For sites with sufficient radiocarbon dates by interpolation each pollen sample is assigned to the corresponding radiocarbon age which makes possible also to determine and correlate chronologically the boundaries of the LPAZs.
The nomenclature for vascular plants follows basically Flora of Republic of Bulgaria (Jordanov et al., 1963-2012) and Guide to Higher Plants in Bulgaria (Kozuharov ed., 1992).
Acknowledgements
I am grateful to all my colleagues and friends from the country and abroad who were involved over several decades in the expeditions to collect materials, their storage, processing, analyses and discussions in the frame of research projects and scientific programs. First of all, I extend my sincere gratitude to my teacher in palynology and co-author Prof. E. Bozilova†, my co-authors Prof. G. Possnert†, Assoc. Prof. E. Marinova, Assoc. Prof. J. Atanassova, Dr. H. Panovska, Assoc. Prof. M. Lazarova, Prof. A. Velchev†, Prof. D. Ivanov, Dr. J. van Huis†, Prof. I. Snowball, Prof. H. Jüngner, Prof. O. Heiri, Prof. A. Lotter, Dr. A. Feurdean, Dr. G. Skog, Dr. I. Vajsov, Prof. D. Pavlova, Assoc. Prof. E. Chakalova, Prof. D. Koleva, Assoc. Prof. G. Popov, Assoc. Prof. I. Velichkov, Prof. G. Hinkov, Prof. Tz. Zlatanov, D. Gyurova with whom high quality papers were published.
Special thanks go to Prof. G. Possnert†, Prof. H. Jüngner, Prof. M. Geyh, Dr. G. Skog and other colleagues who generously provided a considerable number of radiocarbon dates. I am indebted to Prof. H.-J. Beug† who gave me the first lessons in the field how to collect cores with hand-coring equipments during his numerous visits to Bulgaria, for the advices and fruitful discussions. Prof. H. Wright† and Prof. B. Ammann ensured funding and guided with Prof. E. Bozilova† the expedition in 1994 to collect cores from glacial lakes in the Rila and Pirin mountains. In the field I always felt the invaluable help from my colleagues and friends Prof. E. Bozilova†, Prof. H.-J. Beug†, Prof. S. Kozuharov†, Prof. D. Dimitrov, Assoc. Prof. G. Angelov, Assoc. Prof. E. Marinova, Assoc. Prof. M. Lazarova, Prof. A. Velchev†, Assoc. Prof. D. Uzunov, Prof. L. Penev, Prof. D. Ivanov, Prof. M. Anchev†, Assoc. Prof. R. Begy, Dr. G. Wolff, Dr. K. Kossev, D. Gyurova, people from the Rila Nature Reserve Rilomanastirska Gora, Vitosha Nature Park, Sofia University St. Kliment Ohridski, Institute of Biodiversity and Ecosystem Research in Sofia, state foresters, and many others.
From my first steps in modern paleoecological science since the early 1980s I was encouraged and supported by Prof. B. Berglund, Prof. B. Ammann, Prof. G. Lang† and Prof. Y. Vasari† who introduced me to the international scientific paleocommunity. I am indebted also to Prof. E. Grimm† who kindly provided for free the software package Tilia. I thank Assoc. Prof. E. Marinova for her constructive comments on the chapter of the anthropogenic impact. Assoc. Prof. D. Kozuharov, Prof. D. Pavlova, Prof. D. Ivanov, Assoc. Prof. E. Marinova, Prof. R. Bradshaw, Dr. P. Ivanov, E. Komitov and D. Gyurova provided photos of several of the sites studied. The technical assistants D. Stoikova† and N. Mihailova prepared a large part of the samples for pollen analysis.
3. RILA MOUNTAIN3.1 Physico-geographical characteristics and modern vegetation
Rila Mountain which is the highest massif on the Balkans (peak Musala, 2925 m) is located between 41°52’30”-42°21’40”N and 23°01’22”-24°01’E in Southwestern Bulgaria. It has a roughly triangular shape (70 × 60 × 40 km) with an area of 2396 km2. The mountain is bordered on the south and southeast by the Pirin (2914 m) and the Western Rhodopes (2191 m) mountains, and on the west and north by the valleys of several rivers. Inner deep river valleys following the major fault lines divide the massif into four parts: Eastern (2925 m), Northwestern (2731 m), Central (2716 m) and Southwestern (2630 m) (Stoichev, Petrov, 1980) (Fig. 2).
The mountain is built by crystalline rocks of Mesozoic and Pre-Mesozoic age. The granitoids form the central and eastern mountain parts, while the Northwestern Rila and the western fringes of Southwestern Rila are built up mainly of metamorphic rocks, gneisses, schists and amphibolites. Some authors consider that Rila Mountain was glaciated twice in the Pleistocene during the Riss and the Würm glacial stages (Ivanov, 1954; Glovnya, 1958, 1962, 1969, etc.) following the Alpine geochronological scheme of the Quaternary glaciations, and others (Velchev, 1995, 1999, 2014; Tonkov et al., 2008) claim to have found evidence also from an earlier glaciation (Mindel). A monograph which presents an extensive review on the Pleistocene glaciations and the formation of the present-day alpine and subalpine landscapes in Bulgaria was recently published (Velchev, 2020). All authors stick to the opinion that the existing visible glacial landforms (cirques, numerous lakes, different types of moraines and trough valleys) were shaped during the last glaciation.
In the last years, with the application of cosmogenic nuclide dating (10Be) on terminal moraine samples, the extent of the last glaciation in the Rila Mountain was mapped. The largest extent of former glaciers that left moraine deposits was around the time of the Last Glacial Maximum (LGM). Most probably, the maximum extent occurred in two phases, the first around the beginning, and the second around the end of the LGM (24-23 kyr BP and 18-16 kyr BP, respectively), separated by a retreat phase during the coldest and also the driest phase of the glacial stage (Kuhlemann et al., 2008, 2013).
The climate above 1000 m is typical montane characterized by the decrease of the annual air temperature by 0.5°C with each 100-m increase in altitude. At 1800-1900 m where the present upper timber-line runs, the mean January temperature is -6°C and the mean August temperature is 11.4°C. As a result of the predominant directions of the moisture transport, the northwestern and northern slopes at altitudes 1000-1700 m receive 1000-1050 mm/year, while the high peaks above 2500 m about 900 mm/year, most of it snow (Velev, 2002).
In the Rila Mountain from 600 to 1800 m brown mountain-forest soils (Cambisols) are widespread, and above them up to 2200 m are found dark-colored mountain-forest soils (Humic Cambisols). The latter acquire a mosaic character at the transition between the subalpine and alpine belts due to their combination with mountain-meadow soils (Umbrisols) (Ninov, 1997).
According to the last geobotanical zoning, Rila Mountain is included as a separate region within the Illyrian (Balkan) Province of the European Deciduous Forest Area (Bondev, 2002). The vegetation is closest to that in the central European mountains, for which the dominance of silicate terrains and its high altitude are important. The present vegetation of the Rila Mountain is distributed in six vegetation altitudinal belts (Velchev, Tonkov, 1986; Bondev, 1991; Velchev, 2002).
The xerothermic oak belt (up to 600 (700 m)) is clearly expressed on the western, northeastern and southwestern slopes of the mountain. The dominant species are Quercuscerris and Quercusfrainetto, together with Carpinusorientalis, Quercuspubescens, Fraxinusornus, Juniperusoxycedrus, Paliurusspina-christi, Coronillaemerus and Coluteaarborescens. Herb communities dominated by Festucavalesiaca, Poabulbosa and Dichantiumischaemum are found on treeless terrains.
The xeromesophilous oak and hornbeam belt (700-1000 m) occurs on the western and eastern slopes of the mountain, and is characterized by a tree vegetation composed of Quercusdalechampii and Carpinusbetulus with an admixture of Ulmusglabra, Acerplatanoides, Acerpseudoplatanus. Fragments of this vegetation occur up to 1700 m. Stands of Pinusnigra and Ostryacarpinifolia are also found.
The beech belt (1000-1600 m) is fragmented and occupies areas in the northern and western parts of the mountain. The dominant tree is Fagussylvatica, which also forms mixed woodstands with Pinusnigra, Abiesalba and Piceaabies at higher altitudes. Secondary communities of Betulapendula, Populustremula, Agrostistenuis, Festucanigrescens, etc. are also found.
The coniferous belt (1600-(2000) 2200 m) is the most compact and well-developed vegetation belt, composed mainly of forests of Pinussylvestris and Piceaabies. The Balkan endemic Pinuspeuce forms a sub-belt and shapes the timber-line in the western and southern parts of the mountain. Within this belt communities of Abiesalba, Betulapendula, Populustremula, Juniperussibirica and Vacciniummyrtillus also occur.
The subalpine belt (2200 (2000)-2500 m) on northern slopes, particularly in the central and eastern parts, is dominated by the thick impenetrable formation of Pinusmugo (dwarf-pine). On areas, free of dwarf-pine, are found Juniperussibirica, Vacciniummyrtillus, and herb communities dominated by Festucavalida, Festucapaniculata, Festucapicta, Sesleriacomosa, and Nardusstricta. Alnusviridis is mainly restricted to the mountain brooks along the steep, rocky slopes. The arctic-alpine character of the vegetation is indicated by the presence of dwarf-willows such as Salixlapponum, Salixreticulata and Salixwaldsteiniana.
The alpine belt (2500-2925 m) is dominated by the herb communities of Carexcurvula, Festucaairoides, Festucariloensis, Dryasoctopetala, Salixherbaceae, etc. The vegetation of the subalpine and alpine belts is rich in endemics. Most of them are classified as glacial relics that survived the harsh conditions of the glaciations. The present-day vegetation in almost all belts is highly influenced by the anthropogenic activities. In many places the coniferous and deciduous forests were damaged or destroyed to a large extent and the timber-line was artificially lowered.
3.2 Northwestern Rila Mountain – Study sites
The northwestern part of the Rila Mountain occupies 24% of its total area and is rich in cirques and glacial lakes. It provides excellent possibilities for exploring important issues related to the Pleistocene glaciations, the character of the glacial bodies, the relictual glacier formations and the postglacial processes. The cirque of the Seven Rila Lakes is the largest one in the mountain, being elongated and extended in a northerly direction. The group of the lakes is located in a tier on the slope between 2535 and 2095 m. The picture of the Pleistocene glaciations is rather complicated and currently two types of glaciations - mountain valley and ice-cap from the last three glacial epochs can be accepted (Fig. 4). Convincing geomorphological evidence related to Mindel glaciation that covered large areas is documented by the stadial and terminal moraines on the slopes between the Dzerman river and Skakavitsa river, on the water-shed ridge between the basins of the Struma river and Iskar river, and by a number of roche-moutonnee on Suhi Rid. During Riss and Würm other types of glacial forms developed. The valley glaciers had deposited accumulative material (frontal, stadial and basal moraines) in the trough part of the Dzerman river and in the cirque itself. After the retreat of the Würm glacier a system of stadial moraines was formed which had blocked the lakes Babreka and Sedmo Rilsko. Most probably, the lakes in the cirque were free of ice already at the termination of the Late Pleniglacial proved by the start of uninterrupted sedimentation in the lakes and the radiocarbon dates of the lateglacial sediments. During the Younger Dryas stadial rudimentary/embryonic and rock glaciers in the sense of Baltakov (2002) and Hughes et al. (2006) probably developed above 2300-2400 m. The overall picture of the last deglaciation is complicated by the cryogenic processes and the formation of the periglacial relief (Tonkov et al., 2008; Velchev et al., 2011; Velchev, 2020).
490C64A6-BC1A-5C55-8530-D2C3EF0F9C3F
Geomorphological map of the cirque of the Seven Rila Lakes in the Northwestern Rila Mountain (after Tonkov et al., 2008).
This is the uppermost investigated lake at 2216 m (42°12’21”N, 23°19’04.66”E) located in the subalpine belt, surrounded by sparse groups of Juniperussibirica and Pinusmugo within herb vegetation (Figs 3 and 4). The lake collects water from the upper lakes. The inlet is at its southern part while two outlets are in the northern and eastern parts. The length of the lake is 240 m with a mean width of 200 m and a maximum depth of 6.5 m. The shores are flat, at some places marshy, and only the western shore is steep and rocky (Ivanov, 1964) (Fig. 5).
E83A8CB8-FA1B-5EF2-B348-F8DA2D59FE2C
A view of Lake Trilistnika (Photo: S. Tonkov).
https://binary.pensoft.net/fig/1672847
<italic>Coring, lithology and radiocarbon dating</italic>
A sediment core 590 cm long and 5 cm in diameter was recovered with square-rod piston sampler (Wright, 1991) at water depth of 6.3 m. The lithology of the sediments is: 0-430 сm gyttja, 430-500 сm silty clay and 500-590 сm grey silt. The radiocarbon age of 12 bulk sediment samples was determined and the results are shown in Table 1. It can be suggested that the deposition of grey silt had started before 16000 cal. yrs. BP (Tonkov et al., 2006, 2008).
Radiocarbon dates from Lake Trilistnika.
Lab. code
Depth (cm)
14C age (BP)
14C age cal. BP, ±2σ (mid-point)
Material dated
Ua-20688
50-52
1645±40
1690-1410 (1550)
gyttja
Ua-20689
105-107
2605±40
2790-2700 (2745)
gyttja
Ua-21598
150-152
3200±40
3550-3340 (3445)
gyttja
Ua-20690
202-204
3925±40
4450-4230 (4340)
gyttja
Ua-20691
240-242
4560±45
5330-5040 (5235)
gyttja
Ua-20692
308-310
6835±50
7760-7580 (7670)
gyttja
Ua-20693
368-370
8040±55
9150-8650 (8900)
gyttja
Ua-20694
396-398
8825±60
10200-9600 (9900)
gyttja
Ua-21599
457-459
11140±100
13450-12850 (13150)
silty clay
Ua-20696
468-470
11365±75
13500-13000 (13250)
silty clay
Ua-21600
481-483
12110±95
15350-13650 (14500)
silty clay
Ua-21601
489-491
12815±130
15950-14350 (15150)
silty clay
<italic>Pollen analysis</italic>
Pollen analysis was performed at 5-10 cm interval and a percentage pollen diagram is constructed (Fig. 6). A separate pollen diagram of the lateglacial section of the core is also presented (Fig. 6a). On the pollen diagram seven local pollen assemblage zones (LPAZs) are recognized (LT-1 to LT-7) (Figs 6 and 7). Brief descriptions are as follows:
Low values of 15-20% are recorded for the total tree pollen curve (AP), attributed mainly to Pinusdiploxylon-type, Pinuspeuce and Ephedra (distachya-type and fragilis-type). Pollen grains of Juniperus, Betula, Alnus, Corylus and Carpinusbetulus are also determined. The total herb pollen (NAP) content is dominated by Artemisia 40-60%, Chenopodiaceae 20% and Poaceae up to 17%. The presence of Achillea-type, Solidago-type, Apiaceae, Rumex pollen is also recorded.
The most characteristic feature of this zone is the high proportion of Pinusdiploxylon-type 50-55%, accompanied by a slight increase of Pinuspeuce, the appearance of continuous pollen curves for Betula and Alnus, and a decrease of Artemisia and Chenopodiaceae to 20% and 5%, respectively. Pollen grains of Abies, Picea, Corylus, Quercus, Ulmus and Carpinus are also recorded. New herb pollen taxa such as Thalictrum, Ranunculus-type, Cyperaceae and spores of Selaginellaselaginoides and Polypodiaceae appear in the fossil record.
The tree pollen curve sharply declines to 20% and Pinusdiploxylon-type is present with 15-10%. Pollen of Abies, Picea and Ulmus is lacking. The participation of Artemisia and Chenopodiaceae increases again, reaching 45-55% and 15-20%, respectively, accompanied by pollen of Achillea-type, Dianthus-type, Cichoriaceae, Galium-type, Rumex, Apiaceae, etc.
The total tree pollen reaches 90% with a maximum of Betula 10% and an increase for Pinusdiploxylon-type 33% and Pinuspeuce 20-25% is recorded. The same tendency is observed for Quercuscerris-type 17%, Corylus 15-20%, Tilia 12%, Ulmus and Alnus. The first local peak of Abies with 15% is established (level 405 cm). Pollen grains of Fagus, Picea and Vitis are also found. The herb pollen taxa are represented by Poaceae 12%, Artemisia up to 5%, Chenopodiaceae 3%, Rumex 5%, Cichoriaceae, Cirsium-type, Achillea-type, each with 1-2%. Spores of Polypodiaceae show a maxium of 10%.
Pollen of Pinusdiploxylon-type reachs 40%, Abies rises to 30-38% and Pinuspeuce up to 15%. A considerable decrease is registered for Quercuscerris-type, Corylus, Tilia, Ulmus and Betula pollen, while Carpinusbetulus is present with 2-4%. Pollen grains of Fagus are regularly found. The total quantity of herb pollen taxa varies between 8% and 16%.
The pollen curves of Fagus and Picea rise to 10% and 5%, respecively. High values of 35% are recorded for Abies pollen with a subsequent reduction to 18%. The participation of Pinusdiploxylon-type is up to 45-50% and of Pinuspeuce up to 15%. Pollen of Juglans is found for the first time. The main herb pollen taxa are Poaceae 4-6%, Artemisia 2%, Cirsium-type, Ranunculus-type, Dianthus-type. The pollen curve of Plantagolanceolata appears together with pollen of Cerealia-type.
The total tree pollen curve reaches 95%, contributed mainly by Pinusdiploxylon-type 50-55% and Abies 15%, while Pinuspeuce decreases below 5%. In this zone pollen of Fagus 20% and Picea 12% attains maximal values. Significant changes in the frequency and diversity of the herb pollen taxa are not registered, except for the appearance of Secale and Triticum-type pollen grains.
Lake Ribno (site 2)
This lake is situated at 2184 m (42°12’23.95”N, 23°19’23.25”E) in the subalpine belt and an inlet brings water from the upper Lake Trilistnika, while the outlet runs into Lake Sedmo Rilsko (Figs 3 and 4). The lake is 250 m long with a mean width of 140 m and a maximum water depth of 2.5 m. The shores of the lake are flat and are surrounded by sparse groups of Pinusmugo and Juniperussibirica among herb vegetation (Ivanov, 1964). A touristic hut is built on the northern shore close to the outlet. (Fig. 8)
B540EF75-221B-5FA1-96DA-5E66E04EEB19
A view of Lake Ribno (Photo: S. Tonkov).
https://binary.pensoft.net/fig/1672852
<italic>Coring, lithology and radiocarbon dating</italic>
A sediment core 640 cm long and 5 cm in diameter was obtained with square-rod piston sampler (Wright, 1991) from a platform at the deepest part of the lake (Fig. 9). The lithology of the sediments is: 0-425 cm gyttja, 425-505 cm clay/gyttja, 505-540 cm silty clay and 540-640 cm grey silt. The radiocarbon age of 13 bulk sediment samples was determined and the results are shown in Table 2. By extrapolation, with some conditionality, the age of the bottom part of the core can be accepted at c. 18000 cal. yrs. BP (Tonkov et al., 2013).
8CBF6054-3483-5F20-8CD8-B8C0883A939D
Coring at Lake Ribno. From left to right: Prof. D. Dimitrov and Prof. H. Wright† (Photo S. Tonkov).
https://binary.pensoft.net/fig/1672853
Radiocarbon dates from Lake Ribno.
Lab. code
Depth (cm)
14C age (BP)
14C age cal. BP, ±2σ (mid-point)
Material dated
Ua-40623
50-51
2106±30
1995-2150 (2070)
gyttja
Ua-40624
99-100
2569±30
2510-2756 (2630)
gyttja
Ua-40625
186-187
4192±31
4621-4840 (4730)
gyttja
Ua-40626
269-270
6359±37
6575-7741 (7160)
gyttja
Ua-40627
354-355
8540±42
9476-9550 (9510)
gyttja
Ua-40628
395-396
9662±47
10780-11210 (11000)
gyttja
Ua-39221
427
10139±52
11400-12050 (11725)
clay/gyttja
Ua-39222
437
10291±56
11800-12400 (12100)
clay/gyttja
Ua-39223
452
10465±53
12100-12700 (12400)
clay/gyttja
Ua-39224
472
11240±59
12990-13260 (13125)
clay/gyttja
Ua-39225
491
12346±67
14000-14750 (14375)
clay/gyttja
Ua-40629
498-500
12692±67
14650-15250 (14950)
clay/gyttja
Ua-39227
532
13483±155
15450-16650 (16050)
silty clay
<italic>Pollen analysis</italic>
Pollen analysis was performed at 5 cm interval and a percentage pollen diagram is constructed (Fig. 10). The lowermost 40 cm of the core contained no pollen. A separate pollen diagram of the lateglacial section of the core is presented (Fig. 10a). Pollen accumulation rates (PAR) for the major tree/shrub and herb taxa, complimentary to their percentage values, are also calculated (Fig. 11). Occasionally, a few fossil stomata were found on the pollen slides from several sample depths (135, 140, 255, 265 and 375 cm). All of them were identified as Pinus sp. and their presence (*) is indicated on the percentage pollen diagram. Seven local pollen assemblage zones (LPAZs) are recognized (LR-1 to LR-7) (Figs 10 and 7). Brief descriptions are as follows:
Percentage pollen diagram of Lake Ribno – Lateglacial section.
https://binary.pensoft.net/fig/1672856
LPAZ LR-1 (600-512 cm, Artemisia-Chenopodiaceae-Pinus-Poaceae) (18000?-15100 cal. yrs. BP)
The quantity of total tree pollen averages 20% with a short peak of 43% (level 575 cm). The main component is Pinusdiploxylon-type with 18-22%, accompanied by some Pinuspeuce, Betula, Juniperus, partly Corylus, Alnus and Ephedra (distachya-type and fragilis-type). The herb pollen taxa are represented by Artemisia 40-60%, Chenopodiaceae up to 20%, Poaceae up to 10%, Achillea-type, Cichoriaceae, Centaureajacea-type, Galium-type, Rumex, Apiaceae, Brassicaceae, Dianthus-type, etc. The total PAR of tree taxa is c. 500 grains cm-2 yr-1, contributed by Pinusdiploxylon-type 200-400, Juniperus and Betula each with 50. The highest values are established for Artemisia up to 1000, Chenopodiaceae up to 400 and Poaceae 220.
LPAZ LR-2 (512-463 cm, Pinus-Artemisia-Betula-Poaceae) (15100-12900 cal. yrs. BP)
The presence of total tree pollen reaches 60-68%, attributed mainly to Pinusdiploxylon-type 30-40%, Pinuspeuce 10-12%, Betula 6%, Juniperus and Corylus each with 2-3%. Low pollen frequencies are recorded for Quercus (cerris-type and robur-type), Alnus, Carpinusbetulus, Humulus/Cannabis-type. Pollen grains of Abies, Fagus, Picea and Tilia are also determined. Pollen of Artemisia is below 20%, Chenopodiaceae 7%, while Poaceae reaches 10-15%. New herb pollen taxa such as Caltha-type, Hypericum, Geum-type and Gentiana are recorded. The total PAR of tree taxa increases to c. 1000 grains cm-2 yr-1, represented by Pinusdiploxylon-type up to 600, Pinuspeuce 250, Betula 100, Juniperus 60. The PAR of herb pollen taxa decreases, contributed mainly by Artemisia 250, Poaceae 200 and Chenopodiaceae 50-100.
LPAZ LR-3 (463-427 cm, Artemisia-Chenopodiaceae-Poaceae) (12900-11600 cal. yrs. BP)
The total tree pollen curve declines to 25-30%, mainly due to Pinusdiploxylon-type 15%, Pinuspeuce 3%, partly Juniperus 2%, and Betula with less than 5%. Pollen of Abies, Picea, Fagus, Tilia and Ulmus becomes sporadical. The presence of Ephedra pollen (distachya-type and fragilis-type) remains constant. The pollen frequencies for Artemisia 32-40% and Chenopodiaceae 15% increase again, while those for Poaceae slightly decrease. The PAR of tree taxa retains nearly the same values with the exception of Pinuspeuce with 120 grains cm-2 yr-1 and a slight rise of Quercusrobur-type up to 70. The PAR of herb pollen taxa shows maximal values for Artemisia 1500 and Chenopodiaceae up to 600. A tendency of increase for Poaceae, Apiaceae and Brassicaceae is recorded.
LPAZ LR-4 (427-297 cm, Betula-Quercetum mixtum-Corylus-Pinus) (11600-7900 cal. yrs. BP)
The total tree pollen reaches 80%, due to Quercusrobur-type 20%, Quercuscerris-type 15%, Betula 10%, Corylus 10-20%, Tilia 10%, Ulmus 5%, Pinusdiploxylon-type 15-20%, Alnus and Juniperus each with less than 5%. Low proportions of Acer, Fraxinusexcelsior-type, Carpinusbetulus, Ephedra (distachya-type and fragilis-type) pollen are also found. The continuous pollen curve of Abiesappears and rises to 5%. Pollen grains of Fagus and Picea are regularly determined. The herb pollen taxa are represented by Poaceae 15-5%, Artemisia up to 15%, Chenopodiaceae 5%, Achillea-type, Rumex, Cichoriaceae, Ranunculus-type, Brassicaceae, Galium-type each below 3-5%, etc. The total PAR of tree taxa increases gradually to 3000 grains cm-2 yr-1, contributed mainly by Betula 300-500, Quercusrobur-type 600-800, Quercuscerris up to 400 and Corylus 700-900. Among the herb pollen taxa only Poaceae retains values of 250-300, while Artemisia and Chenopodiaceae sharply decline. The increase of Apiaceae and Brassicaceae up to 100 each is worth to be mentioned.
LPAZ LR-5 (297-223 cm, Pinus-Abies) (7900-5800 cal. yrs. BP)
Pollen of Abies reaches 25-30%, Pinusdiploxylon-type 30-35% and Pinuspeuce 12%. Pollen frequencies of deciduous trees like Betula, Quercusrobur-type, Quercuscerris-type, Corylus, Tilia and Ulmus decline, while Carpinusbetulus is present with 2-4%. Pollen of Fagus, Picea and Carpinusorientalis/Ostrya is continuously found. Significant changes in the participation of the herb pollen taxa are not recorded, except for the appearance of single grains of Plantagolanceolata, Urtica, Cerealia-type. This zone marks the rise of PAR for the coniferous trees such as Pinusdiploxylon-type up to 1500 grains cm-2 yr-1, Abies 1000, Pinuspeuce 500, while the values of the deciduous trees gradually decline.
LPAZ LR-6 (223-133 cm, Pinus-Abies-Fagus-Picea) (5800-3400 cal. yrs. BP)
Pollen of Pinusdiploxylon-type rises to 40-45%, Abies is present with 15-30%, Pinuspeuce with 10%, Fagus up to 10%. A continuous pollen curve of Picea below 5% appears. A slight increase of Betula and Carpinusbetulus is recorded. Pollen grains of Juglans are quite common. The main herb pollen taxa are Poaceae 5%, Artemisia, Cichoriacae, Rumex, Ranunculus-type, Apiaceae, Brassicaceae, Plantagomajor/media-type, etc. Pollen grains of Plantagolanceolata, Cerealia-type, Urtica are also recorded. The tendency of an increase for the PAR of trees is visible, attributed to Pinusdiploxylon-type with up to 3000 grains cm-2 yr-1, Abies 1500-1750, Pinuspeuce 750 and Fagus 500. Among the herb pollen taxa attention deserves Poaceae with 250-300.
LPAZ LR-7 (133-0 cm, Picea-Fagus-Pinus-Abies) (3400 cal. yrs. BP-until present)
The pollen curve of Picea rises to 15% together with Fagus 20% while Abies declines to 8%. High pollen values are recorded for Pinusdiploxylon-type 50-55% and Pinuspeuce 10-15%. The last finds of Ephedrafragilis-type pollen are recorded. A slight increase for Corylus, Quercus and Alnus pollen is established. Important changes in the frequency and diversity of the herb pollen taxa are not registered. In this uppermost pollen zone maximal PAR of the following trees are recorded: Pinusdiploxylon-type 3500 grains cm-2 yr-1, Pinuspeuce 1250, Fagus 1000 and Picea 750.
Lake Sedmo Rilsko (site 3)
The lowest located Lake Sedmo Rilsko is situated at 2095 m (42°12’39.51”N, 23°19’32.35”E) in the subalpine vegetation belt just above the present timber-line (Figs 3 and 4). The lake collects water from all upper lakes. The shores are flat and only the southeastern slope is steep and rocky. The lake is about 330 m long and 180 m wide, with a maximum water depth of 11 m (Ivanov, 1964). It is surrounded by groups of Pinusmugo and Juniperussibirica within patches of herb vegetation. Not far away, to the north, are found single trees of Pinuspeuce, Pinussylvestris and Piceaabies (Bozilova, Tonkov, 2000, 2011) (Fig. 12).
1D7949D6-4AC4-5104-8C9B-A9BBBD38F635
Pollen accumulation rates (PAR; pollen grains cm-2 yr-1) for the main tree/shrub and herb taxa from Lake Ribno plotted against age in cal. yrs. BP.
https://binary.pensoft.net/fig/1672858
<italic>Coring, lithology and radiocarbon dating</italic>
A sediment core 520 cm long and 5 cm in diameter was obtained from a platform at the central part of the lake at water depth of 8.25 m with square-rod piston sampler (Wright, 1991). The lithology of the sediments is: 0-415 cm brown gyttja, 415-435 cm grey clay, 435-485 cm olive gyttja and 485-520 cm grey silt. The radiocarbon age of 8 samples (3 of plant macrofossils and 5 of bulk sediment) was determined and the results are shown in Table 3.
Radiocarbon dates from Lake Sedmo Rilsko.
Lab. code
Depth (cm)
14C age (BP)
14C age cal. BP, ±2σ (mid-point)
Material dated
UtC-6057
225
4006±48
4790-4290 (4540)
Pinus sp. shoot
UtC-6095
355
6480±80
7570-7250 (7410)
Betula fruit and Pinus sp. needle
UtC-6058
410
10170±60
12110-11500 (11805)
plant tissue
LuS-8991
435-437
10840±75
12910-12630 (12770)
gyttja
DeA-24386
442.5
11306±43
13260-13070 (13165)
gyttja
DeA-24388
452.5
12140±46
14160-13820 (13990)
gyttja
LuS-9336
458-460
12640±70
15270-14690 (14980)
gyttja
LuS-9337
470-472
12920±75
15720-15190 (15455)
gyttja
<italic>Pollen analysis</italic>
Pollen analysis was performed at 2.5-5 cm interval and a percentage pollen diagram is constructed (Fig. 13). A separate pollen diagram of the lateglacial section of the core is also presented (Fig. 13а). On the pollen diagram seven local pollen assemblage zones (LPAZs) are recognized (LSR-1 to LSR-7) (Figs 13 and 7). Brief descriptions are as follows:
LPAZ LSR-1 (520-457 cm, Artemisia-Chenopodiaceae-Poaceae-Pinus) (17000?-14750 cal. yrs. BP)
This zone is characterized by low values of the total tree pollen c. 15-20%, attributed mainly to Pinusdiploxylon-type, Pinuspeuce, and partly Betula, Juniperus and Ephedra (distachya-type and fragilis-type). The herb pollen taxa dominate, among them Artemisia with up to 47%, Chenopodiaceae 20%, Poaceae 15-20%, and others such as Achillea-type, Galium-type, Rumex, Brassicaceae, Apiaceae.
LPAZ LSR-2 (457-437 cm, Pinus-Artemisia-Poaceae-Betula) (14750-12800 cal. yrs. BP)
The total tree pollen curve steeply reaches a maximum of 60-70% and then declines to 35%. The most abundant tree taxa are Pinusdiploxylon-type up to 50%, Pinuspeuce 10%, Betula 10%, Quercusrobur-type 5%, Ulmus, Tilia, Carpinusbetulus, Corylus. Among the herb pollen taxa should be mentioned Artemisia 20%, Poaceae 15%, Chenopodiaceae 5%, Achillea-type, Rumex, Galium-type, Thalictrum, Apiaceae, etc.
LPAZ LSR-3 (437-407 cm, Artemisia-Poaceae-Chenopodiaceae) (12800-11600 cal. yrs. BP)
Pollen of Artemisia reaches 35%, Chenopodiaceae 15%, Poaceae 20%, Achillea-type, Rumex and Galium-type each with 5%. The total tree pollen curve declines to a minimum of 15% and subsequently rises to 50%, attributed to Betula 10-20%, Pinusdiploxylon-type 10%, Quercuscerris-type, Quercusrobur-type and Corylus each with less than 5%, Pinuspeuce and Juniperus with 2-3%.
LPAZ LSR-4 (407-358 cm, Betula-Quercetum mixtum-Pinus) (11600-8000 cal. yrs. BP)
In this zone the total tree pollen curve increases to 70-85%, contributed by Betula 27%, Quercusrobur-type 5-35%, Quercuscerris-type 3-15%, Corylus 5-7%, Alnus 2-3%, partly Ulmus and Tilia each with 5%. The participation of Pinusdiploxylon-type reaches 15% and of Pinuspeuce 5%. Pollen grains of Carpinusbetulus, Acer, Fraxinus and Fagus are also recorded. Both pollen types of Ephedra disappear. The participation of Artemisia 5%, Chenopodiaceae 2%, Poaceae 10%, Achillea-type, Rumex, Galium-type, Ranunculus-type and other herb pollen taxa declines. Spores of Polypodiaceae are present with 5%.
LPAZ LSR-5 (358-230 cm, Pinus-Abies-Quercetum mixtum-Corylus) (8000-4750 cal. yrs. BP)
In this zone the dominance of deciduous tree pollen represented by Betula 10-2%, Quercusrobur-type 25-5%, Corylus 20-5%, Ulmus and Tilia is replaced by Pinusdiploxylon-type up to 25-35% and Pinuspeuce with 28%. Another change is the quick increase of Abies pollen up to 20-30%. A continuous pollen curve of Fagusappears with 1-2%. Single pollen grains of Picea, Carpinusorientalis/Ostrya, Hedera and Vitis are also recorded. Important changes in the participation of the herb pollen taxa are not established.
LPAZ LSR-6 (230-163 cm, Pinus-Abies-Fagus) (4750-3200 cal. yrs. BP)
The pollen curve of Fagus displays a rapid increase to 12%, accompanied by the appearance of Picea pollen with 2-3%. The pollen curve of Pinusdiploxylon-type retains its values of 30-35%, Pinuspeuce 15-20%, and Abies 20%. Deciduous tree taxa such as Quercuscerris-type, Quercusrobur-type, Betula, Corylus and Carpinus are present with low pollen frequencies. In this zone begins the pollen curve of Plantagolanceolata.
LPAZ LSR-7 (163-0 cm, Picea-Pinus-Fagus) (3200 cal. yrs. BP-until present)
The most characteristic features are the maximum of 15% attained by Picea and the rise of the pollen curves of Pinuspeuce and Pinusdiploxylon-type up to 25% and 35%, respectively. A slight increase for Juniperus, Betula, Corylus and Quercusrobur-type pollen is observed. Pollen grains of Juglans are regularly found. Pollen of Cerealia-type, Triticum-type and Secale appear in this zone. Higher values are recorded for Rumex, Plantagolanceolata, Scleranthus, Poaceae and Artemisia pollen.
Lake Skakavitsa (site 4)
This lake is located at 2170 m (42°12’53.19”N, 23°18’14.30”E) in the lower part of the subalpine belt (Fig. 3). It lies in a shallow cirque and has an elongated shape narrowing in its northern part. The lake is about 250 m long, 60 m wide and 3 m deep with a total area of 1 ha. The western shore is rocky and steep and the others are flat. It is surrounded by dense stands of Juniperussibirica, Pinusmugo, Vacciniumuliginosum and herb communities on open areas. The inlet lies to the south and the outlet to the north where starts the beginning of the Skakavitsa river (Fig. 14). The main components of the herb vegetation are Sphagnumcapillifolium, Polytrichumcommune, Bistortavivipara, Empetrumnigrum, Homogynealpina, Carexrostrata, Alopecurusgerardii, Nardusstricta, Potentillaerecta, Geumcoccineum, Pseudorchisalbida, Gentianellabulgarica, Primulafarinosa, Bruckenthaliaspiculifolia, etc. (Lazarova et al., 2024)
C5C0F913-9DF7-5A58-96AD-1E48A6C2923E
Percentage pollen diagram of Lake Sedmo Rilsko – Lateglacial section.
https://binary.pensoft.net/fig/1672861
<italic>Coring, lithology and radiocarbon dating</italic>
The sediment core 120 cm long was taken from a marginal peat land in the shallow south-eastern part of the basin with a Livingstone hand-corer. The lithology of the sediments is: 0-20 cm peat, 20-80 cm decomposed peat, 80-119 cm gyttja, 119-120 cm grey sandy clay. The radiocarbon age of 3 bulk sediment samples was determined and the results are shown in Table 4. The age of the bottom part of the core is c. 3700 cal. yrs. BP.
Radiocarbon dates from Lake Skakavitsa.
Lab. code
Depth (cm)
14C age (BP)
14C age cal. BP, ±2σ (mid-point)
Material dated
LuS-9333
77-78
2085±50
2300-1890 (2095)
peat
LuS-9334
88-90
2420±50
2710-2340 (2525)
gyttja
LuS-9335
117-119
3440±50
3840-3560 (3700)
gyttja
<italic>Pollen analysis</italic>
Pollen analysis was conducted at 5 cm interval and a percentage pollen diagram is constructed (Fig. 15). Pollen accumulation rates (PAR) for the major tree/shrub and herb taxa are also calculated (Fig. 16). On the pollen diagram four local pollen assemblage zones (LPAZs) are recognized (Sk-1 to Sk-4). Brief descriptions are as follows:
Pollen accumulation rates (PAR; pollen grains cm-2 yr-1) for the main tree/shrub and herb taxa from Lake Skakavitsa plotted against age in cal. yrs. BP.
https://binary.pensoft.net/fig/1672864
LPAZ Sk-1 (120-103 cm, Pinus-Abies-Picea) (3780-3070 cal. yrs. BP)
Tree pollen dominates with 77-80%. Pollen grains of Pinusdiploxylon-type are present with 31-39%, followed by Abies 18-23%, Picea up to 9.3%, Pinuspeuce 3-4%. Deciduous pollen of Quercus, Tilia, Corylus, Carpinus, Fagus is each below 5%. The first pollen grains of Juglans are recorded. The main herb pollen taxa are Poaceae up to 6.2%, Dianthus-type up to 2.1%, Ranunculaceae 1.3%, Taraxacum-type (Cichorioideae) 1.2%, Chenopodiaceae, Achillea/Aster-type, Artemisia, Plantago, Cerealia-type each below 1%. The local elements are pollen of Cyperaceae 1.5%, spores of Polypodiaceae and Selaginellaselaginoides. The total PAR of tree taxa is between 3200 and 8000 grains cm-2 yr-1, contributed by Pinusdiploxylon-type 1400-4600, Abies 900-2000, Picea 130-930, Pinuspeuce 150-490, Juniperus up to 530, etc. The total PAR of herb taxa is 1600-2500 with the highest values for Poaceae 180-700.
LPAZ Sk-2 (103-58 cm, Pinus-Picea-Abies-Poaceae) (3070-1560 cal. yrs. BP)
The total tree pollen curve slightly declines to 60% (level 100 cm). The participation of Pinusdiploxylon-type is 24.5-35.5%, Abies 10%, Picea 14.3%, Pinuspeuce 2-6%. A characteristic feature is the appearance of the pollen curve of Fagus which rises to 3.6%. Pollen of Poaceae reaches a maximum of 13.4% accompanied by Cerealia-type up to 3%, Taraxacum-type 2.3%, Artemisia and Ranunculaceae each with 2.2%, Dianthus-type 2%, Apiaceae and Achillea/Aster-type each with 1.7%. Important changes in the frequency and diversity of the local plants are not registered except for the presence of Sphagnum spores. The tendency of increase of the total tree PAR is visible by the maximal values of 15000-18000 grains cm-2 yr-1, attributed to Pinusdiploxylon-type from 3000 to 7000-8800, Picea 2000, Pinuspeuce 1000, Quercus up to 1200, Fagus 1000. The total herb PAR also rises to 5000-9000 and the highest values are recorded for Poaceae 1100-1700, Cerealia-type 200-400, Taraxacum-type up to 600, Ranunculaceae 600, Achillea/Aster-type 450, Apiaceae 400.
LPAZ Sk-3 (58-28 cm, Pinus-Picea-Fagus) (1560-740 cal. yrs. BP)
The total tree pollen curve increases again from 69% to 82%, contributed mainly by Pinusdiploxylon-type 23-33.8%, Picea with a maximum of 23.3%, Fagus up to 4.5%, Abies 7.8%, Pinuspeuce 3.8%. Pollen of deciduous tree taxa slightly rises as shown by Quercus up to 5.6%, Alnus 2.5%, Corylus 2.3%. Pollen of Juglans is regularly found. Among the herb pollen taxa Poaceae decreases to 3.6%. The rest of the herb and local pollen taxa display no significant changes in their participation, except a slight increase of Sphagnum spores up to 2.3%. The total PAR of tree taxa declines from 18000 to 12500 grains cm-2 yr-1, attributed to Pinusdiploxylon-type 6500-5000, Abies 1800-600, Pinuspeuce 400, Alnus 650-150. Stable values are recorded for Piceac. 3000 and Fagus 1000-800. The total PAR of herb taxa decreases from 8500 to 2500 as shown by Poaceae 1250-500, Taraxacum-type 800-200, Artemisia 400-100, etc.
LPAZ Sk-4 (28-0 cm, Pinus-Picea-NAP) (740 cal. yrs. BP-until present)
The total tree pollen is c. 70% represented by Pinusdiploxylon-type 33-36.4%, Picea 10%, Quercus up to 6.4%, Fagus 4.3%, Pinuspeuce up to 3%, etc. The participation of herb taxa increases to 37%, contributed by Poaceae 7%, Taraxacum-type 3.6%, Cerealia-type 2.2%, Artemisia 2.8%, Plantago 2.2%, Brassicaceae 1.9.%, etc. Among the local plants can be mentioned Cуperaceae 3%, Carex 1.8% and the spores of Sphagnum up to 5.3%. The total tree PAR is c. 12500 grains cm-2 yr-1, a bit lower compared to the previous zone, contributed by Pinusdiploxylon-type 5000-8000, Pinuspeuce 600-300, Abies 900-250, Picea 1000-2000 and Fagus 1000-600. Higher values are recorded for Quercus 1000-1200. The total PAR of the herb taxa varies between 5000 and 6000, attributed to Poaceae 1000-1250, Cerealia-type 300-500, Taraxacum-type c. 500, etc.
Lake Panichishte (site 5)
This lake is located at 1370 m (42°15’45.67”N, 23°17’38.97”E) in the lower range of the coniferous forest belt (Fig. 3). It is one of the few lakes in the mountain with tectonic origin. The lake has an elliptic shape and occupies an area of 1.2 ha. The maximal water depth is 4 m. The lake is surrounded by a dense forest composed of Pinussylvestris and Piceaabies, with some Abiesalba, Pinuspeuce and Fagussylvatica. The peripheral parts of the lake are overgrown by various hygrophytes and most of the water surface is covered by Potamogetonnatans. The open areas close to the shores are highly ruderalized (Bozilova et al., 2002; Tonkov et al., 2020). (Fig. 17)
7BB73F63-0ABC-5388-9DB4-E3CDF7BCC15D
Coring at Lake Panichishte. From left to right: Prof. L. Penev, Assoc. Prof. D. Uzunov and Prof. D. Dimitrov (Photo S. Tonkov).
https://binary.pensoft.net/fig/1672865
<italic>Coring, lithology and radiocarbon dating</italic>
Two sediment cores P-2 and P-3, both 5 cm in diameter, were obtained from the central part of the lake with square-rod piston sampler (Wright, 1991). The Core P-2 with a length of 150 cm was collected at water depth of 1.7 m and selected for pollen and plant macrofossil analyses. The lithology of the sediments is: 0-50 cm peat with sand and plant remains and 50-150 cm peaty gyttja. The Core P-3 with a length of 115 cm was collected at water depth of 2 m and was analysed for pollen content. The lithology of the sediments is: 0-50 cm coarse peat with plant remains and 50-115 cm peaty gyttja. The radiocarbon age of 9 bulk sediment samples was determined and the results are shown in Table 5. The age of both cores covers c. the last 2000 years.
Radiocarbon dates from Lake Panichishte.
Lab. code
Depth (cm)
14C age (BP)
14C age cal. BP, ±2σ (mid-point)
Cal. AD (mid-point)
Material dated
Core P-2
Hel-4375
30-35
870±100
980-650 (815)
970-1300 AD (1135AD)
peat with plant remains
Hel-4376
75-80
1340±90
1420-1010 (1215)
530-940 AD (735AD)
peaty gyttja
Hel-4377
145-150
1950±90
2140-1630 (1885)
190BC-320 AD (65AD)
peaty gyttja
Core P-3
Ua-61843
10
160±29
290-40 (165)
1660-1910 AD (1785AD)
peat with plant remains
Ua-61844
35
388±29
510-320 (415)
1440-1630 AD (1535AD)
peat with plant remains
Ua-61845
50
673±30
680-550 (615)
1270-1400 AD (1335AD)
peaty gyttja
Ua-61846
70
1349±31
1320-1180 (1250)
630-770 AD (700AD)
peaty gyttja
Ua-61847
90
1643±30
1620-1410 (1515)
330-540 AD (435AD)
peaty gyttja
Ua-61848
110
1908±31
1930-1740 (1835)
20-210 AD (115AD)
peaty gyttja
<italic>Pollen analysis</italic>
The cores were sampled at 5-10 cm interval and two pollen diagrams are constructed (Figs 18 and 19). Pollen accumulation rates (PAR) for the major tree/shrub and herb taxa from Core P-3 are also calculated (Fig. 20). The palynostratigraphical correlation of both cores is feasible due to the similarities in the behaviour of the main pollen curves and the application of the depth/age models constructed by linear interpolation. Three local pollen assemblage zones (LPAZs) are recognized (LP-1 to LP-3). Brief descriptions are as follows:
6FD225D8-AF96-51B5-ABD2-BA89B25ED4E2
Percentage pollen diagram of Lake Panichishte (Core P-2).
Pollen accumulation rates (PAR; pollen grains cm-2 yr-1) for the main tree/shrub and herb taxa from Lake Panichishte (Core P-3) plotted against age in cal. yrs. BP.
Tree pollen dominates, attributed mainly to Pinusdiploxylon-type 15-25%, Fagus 20-30%, Abies 10-20%. Comparatively low pollen frequencies below 5% are registered for Pinuspeuce, Picea, Juniperus, Corylus, Quercuscerris-type, Quercusrobur-type, Carpinusbetulus, Ulmus, etc. A sharp maximum of Betula pollen with 20% is recorded at the transition to the next zone (Fig. 18), accompanied by a decline of Fagus and a rise of Pinusdiploxylon-type. The herbs are represented by Poaceae 5-7% and a variety of taxa, including hydrophytes and hygrophytes such as Typha/Sparganium-type, Typhalatifolia, Potamogeton, Myriophyllum, and Cyperaceae with 15%. The total PAR of tree taxa is c. 6000 (maximum 10000) grains cm-2 yr-1, contributed by Pinusdiploxylon-type 2000, Pinuspeuce 200-300, Abies 1000, Fagusc. 1500, Quercuscerris-type 600-800, Picea below 250. The total PAR of herb taxa is 1000-1500, attributed mainly to Poaceae 500-750.
The domiant pollen type is Pinusdiploxylon with 35-40%. Pollen of Abies, Fagus and Picea is present with 5-15%, 10% and 5%, respectively. Pollen of Juglans is also found. The anthropogenic pollen indicators are represented by Plantagolanceolata, Plantagomajor/media-type, Rumex, Polygonumaviculare-type and Secale, Triticum-type, Cerealia-type. Significant changes in the pollen frequencies of the local taxa are not established. The total PAR of tree taxa declines to 2000-3000 grains cm-2 yr-1, contributed by Pinusdiploxylon-type 1000-2000, Pinuspeuce 100, Abies and Fagus each below 500, Picea 250, Betula 200-400. The total PAR of herb taxa is below 500, attributed mainly to Poaceae.
The most characteristic feature is the rise of Picea pollen curve up to 15%, accompanied by Pinusdiploxylon-type 40-70%, Abies 18%, Fagus 10%, Pinuspeuce 5%, Corylus up to 10%. The herb pollen taxa are represented by Poaceae 10%, Achillea-type, Cichoriaceae, Plantagolanceolata, Rumex, Polygonumaviculare, etc. The total PAR of tree taxa increases again to 8000-9000 grains cm-2 yr-1, attributed to Pinusdiploxylon-type 2000-2500, Picea up to 1250, Pinuspeuce 300-400, Abies and Fagus each up to 500. The total PAR of herb taxa varies between 1500 and 2000, contributed by Poaceae 500, Chenopodiaceae 100-150, Polygonumaviculare 200 and Plantagolanceolata 100.
<italic>Plant macrofossil analysis</italic>
The samples for plant macrofossil analysis were taken from Core P-2 at 10 cm interval with a volume of 50 cm3 and analyzed with a binocular at magnification 10-80×. The plant remains are presented in absolute numbers on a macrofossil diagram (Fig. 21) (Bozilova et al., 2002; Marinova, Tonkov, 2003). The results allow to distinguish three local macrofossil assemblage zones (LMAZs) and their description (LPM-1 to LPM-3) is briefly as follows:
1A22A5EE-BB57-54A3-AA42-BA6D7E18656E
Plant macrofossil diagram of Lake Panichishte (Core P-2).
https://binary.pensoft.net/fig/1672869
LMAZ LPM-1 (140-85 cm) (1800-1290 cal. yrs. BP)
Plant remains from coniferous and deciduous trees are determined in almost all samples. Needles/fragments of needles and cone scales of Abiesalba and Pinussylvestris prevail. Fruits of Betula and cupules of Fagussylvatica are also found. Needles of Pinuspeuce appear in the upper part of the zone. The macrofossil record is rich in seeds of telmatic, submerged and floating plants such as Veronica sp., Potentilla sp., Glyceriafluitans, Carexvesicaria, Carexriparia, Juncusatrata-type, Schonoeplectuslacustris, Potamogetonnodosus, Potamogetonnatans, Sparganiumerectum, Myriophyllumspicatum.
LMAZ LPM-2 (85-30 cm) (1290-750 cal. yrs. BP)
Needles of Abiesalba and fruits of Betula are recorded in several samples. The quantity of Carexvesicaria friuts increases. A characteristic feature is the nearly complete absence of seeds and fruits from hydrophytes such as Potamogetonnatans, Potamogetonnodosus and Myriophyllumspicatum. Plant macroremains from trees are lacking in the upper part of the zone. Charcoal particles are found.
Male cones of Piceaabies, few needles of Abiesalba and fruits of Betula and Fagussylvatica are determined in the uppermost sample. The quantity of seeds and fruits from Sparganiumerectum, Juncus sp. and Potamogetonnatans increases. Charcoal fragments are also established.
3.3 Vegetation history in the Northwestern Rila MountainLateglacial
The age of the sediment cores from the lakes studied in the cirque of the Seven Rila Lakes is assumed to be older than 15000-16000 cal. yrs. BP, so that part of the Late Pleniglacial is also represented (Fig. 7). The exact time when the lakes were free of ice and grey silt started to accumulate could not be defined as attempts to obtain radiocarbon dates from the bottom parts of the cores were not successful. However, it could be suggested that the local cirque glacier retreated above 2300-2400 m after the end of the Last Glacial Maximum c. 19000 cal. yrs. BP (Tonkov et al., 2008).
The length of the lateglacial sections varies from 158 cm for Lake Trilistnika (Fig. 6a) to 173 cm for Lake Ribno (Fig. 10a) and 113 cm for Lake Sedmo Rilsko (Fig. 13a). Before the termination of the Late Pleniglacial c. 14700 cal. yrs. BP the biostratigraphy of the pollen zones LT-1, LR-1 and LSR-1 indicates typical glacial conditions at high-mid altitudes. Open herb vegetation of “mountain-steppe” character or alpine tundra in the sense of Jalut et al. (2005) dominated by Artemisia, Chenopodiaceae, Poaceae and various cold-resistant and heliophilous species from Achillea, Centaurea, Rumex, Thalictrum, Galium, Dianthus, Plantago, Brassicaceae, etc. was widely distributed. This vegetation pattern comprised also isolated stands of pines (Pinusmugo, Pinussylvestris and Pinuspeuce) and shrubland of Juniperus-Ephedra. Interest attaches to the find of Ephedrafragilis pollen complementary to Ephedradistachya. Both species were important constituents of the lateglacial flora and inhabited open sandy places. Today Ephedrafragilis ssp. campylopoda occurs in only one place in Bulgaria, along the Struma river valley, and has not been reported for the Rila Mountain. The identification of pollen grains of trees other than Pinus such as Quercus, Corylus, Carpinusbetulus, Alnus, Abies, Fagus, Picea, though in minimal quantities, suggests their probable survival at lower altitudes in sheltered habitats (refugia) with deep soils, sufficient moisture and favorable temperature for growth. Therefore, in the absence of a dense forest cover, the find of deciduous tree pollen in the lateglacial lake sediments is not unusual, and the possible re-bedding in the hard grey silt is most unlikely. Differently, other authors accept possible re-deposition of deciduous tree pollen in the lateglacial sediments from unknown deposits as in the case of Lake Kremensko-5 (2124 m) in the Northern Pirin Mountain (Atanassova, Stefanova, 2003).
Based on the increase of tree pollen and the decline of Artemisia and Chenopodiaceae, it can be concluded, that the tendency to warmer climate started after 16000 cal. yrs. BP. This trend appears in good conformity with the isotopic signal from ice-cores, the Netherlands and the Alps at the end of Greenland Stadial 2, preceding the Bölling/Alleröd interstadial complex (de Klerk, 2004) (Fig. 22)
EFBE00DF-BF7F-5DBF-8EEA-1C776933652D
Comparison of the lateglacial palynostratigraphy and chronology of the lakes studied in the Northwestern Rila Mountain with the lateglacial δ18O record and event stratigraphy from the GRIP Greenland ice-core (modified after Tonkov et al., 2011).
https://binary.pensoft.net/fig/1672870
The pollen assemblages after c. 15000 cal. yrs. BP point unequivocally to an initial stage of afforestation with pines (Pinusmugo, Pinussylvestris and Pinuspeuce) and Betula in the approaches to the lakes. The pine-birch stands restricted the distribution of the herb “mountain-steppe” vegetation and at lower altitudes deciduous trees (Quercus, Carpinusbetulus, Corylus) spread from their local refugia as the climate became warmer. The radiocarbon dates of 12692±67 14C yrs. BP (Table 2) and 12640±70 14C yrs. BP (Table 3) mark the establishment of interstadial vegetation with a maximal spread of trees c. 14000 cal. yrs. BP. The deposition of clay/gyttja, richer in organic content, as shown by loss-on-ignition analysis of the lateglacial sediments from Lake Sedmo Rilsko serves also as an indication for a change in the trophic conditions of the lakes and for a higher bioproductivity of the surrounding vegetation (Lotter, Hofmann, 2003).
The time interval identified with pollen zones LT-2, LR-2 and LSR-2 (Figs 6a, 10a and 13a) can be successfully correlated with the Bölling/Alleröd interstadial complex from Western Europe. Oxygen isotope studies from Switzerland (Lotter et al., 1992; Ammann et al., 1994) and The Netherlands (Hoek, 1997; Hoek, Bohncke, 2001) indicated a major temperature rise around 12600/12450 14C yrs. BP with a simultaneous expansion of (shrub) forests according to the paleobotanical data.
It is reasonable to compare the local vegetation development and radiocarbon chronology with the palaeoclimatic signal from Greenland ice-cores due to their very high stratigraphic and temporal resolution and precise dating (INTIMATE event stratigraphy- INTegrating Ice-core, MArine, and TErrestrial records) (Rasmussen et al., 2014) (Fig. 22). The event stratigraphies divide the characteristic sequence of Greenland climate changes in the Lateglacial and Early Holocene periods into numbered Greenland Stadials (GS) and Greenland Interstadials (GI). Following the age-depth models the distinct rise of Betula, Pinus (Pinuspeuce, Pinusdiploxylon-type) and Juniperus pollen after c. 15000 cal. yrs. BP is close to the oxygen-isotope shift with a prominent rise in temperature at the start of GI-1e at 14700 ice-core years before present recorded in the GISP2 core (Stuiver et al., 1995) and at 14700 ice-core years in the GRIP ice-core (Bjorck et al., 1998). The colder periods GI-1d (14070-13950 cal. yrs. BP) and GI-1b (13300-13100 cal. yrs. BP) of the Greenland Interstadial with shorter duration were not identified in the lateglacial pollen sequencies from the Northwestern Rila Mountain, probably because the existing vegetation cover was not influenced by such short-lived climate fluctuations. However, the decline of total tree (shrub) pollen, mainly for Pinus and Betula, after c. 13200 cal. yrs. BP indicates a cooling trend at the end of the lateglacial interstadial at 12900 cal. yrs. BP.
The lateglacial pollen records point to a reversal towards stadial conditions in the Rila Mountain and the stratigraphic interval, identified with the pollen zones LT-3, LR-3 and LSR-3 (Figs 6a, 10a and 13a), can be correlated with the last cold phase at the termination of the Lateglacial, the Younger Dryas stadial (Alley, 2000). The drop in temperature and precipitation favored the re-advance of the herb “mountain-steppe” vegetation and trees have moved downslope. Several radiocarbon dates were obtained for this stadial phase, namely from Lake Ribno (Table 2), which aid support in the interpretation of changes in vegetation and climate. The transition from the Bölling/Alleröd interstadial complex to the Younger Dryas stadial has occurred c. 13000/12900 cal. yrs. BP. This result comes in good conformity with the ice-core event GS-1 (Greenland Stadial 1), the Younger Dryas cold event (12900-11700 cal. yrs. BP). Indications for a climate warming after 12100 cal. yrs. BP, following the most unfavorable environmental conditions c. 12500 cal. yrs BP, are manifested by the rise of the tree pollen curve and the decline for Artemisia and Chenopodiaceae (Fig. 10a). The transition to Holocene at c. 11700/11600 cal. yrs. BP is clearly marked by the steep rise of the quantity of tree pollen, attributed mainly to Pinus, Betula, Quercus, Corylus, Carpinusbetulus, and a sharp decline for Artemisia and Chenopodiaceae.
The lateglacial vegetation reconstruction in response to climate fluctuations is supplemented by the PAR of the main tree (shrub) and herb taxa established from Lake Ribno (Fig. 11). The dominance of the herb “mountain-steppe” vegetation at high-mid altitudes is clearly visible throughout the entire Lateglacial with a partial retreat during the Bölling/Alleröd interstadial complex (Greenland Interstadial I).
Holocene
The Holocene vegetation succession in the study area followed several stages determined by the migration and expansion rates of the main deciduous and coniferous trees influenced by the climatical, ecological and anthropogenical factors. The time span of these stages and their approximate age ranges are based on the local radiocarbon chronology established (Fig. 7).
The onset of the Holocene was characterized by a quick amelioration of the climate which caused a restriction of the herb “mountain-steppe” vegetation and triggered the initiation of the re-forestation processes. Also, a change of the type of sediment from clay to gyttja deposited in the glacial lakes has occurred (Lotter, Hofmann, 2003). The first Holocene vegetation stage lasted between 11700/11600 and 8000/7900 cal. yrs. ВР (pollen zones LT-4, LR-4 and LSR-4) and within it two phases can be distinguished. The duration of the first phase is estimated at c. 1500-1600 years when pioneer forests of Betula occupied the mountain slopes at mid-higher altitudes on barren soil replacing in many areas the remnants of the lateglacial herb vegetation. A pronounced decline of Artemisia, Chenopodiaceae, Poaceae, Achillea, Aster and other herb taxa is observed but they still continued to occupy a great share of the area around the lakes. In the close vicinity to the cirque the birch forests were sparser, accompanied by stands of pines (Pinusmugo, Pinussylvestris and Pinuspeuce), Alnus (most probably Alnusviridis) and Juniperus shrubland. The presence of Pinus sp. was confirmed by the find of fossil stomata in the sediments of Lake Ribno c. 10000 cal. yrs. BP (Fig. 10). The pollen assemblages reflect also the beginning of widespread of mixed oak forests (Quercetum mixtum) with abundant Tilia, Ulmus, Fraxinusexcelsior and Acer below the birch zone. These forests reached their maximal distribution c. 10000-9800 cal. yrs. ВР, which marked the commencement of the second phase, when Corylus started to expand in the study area. The absence of a dense forest cover above the deciduous tree zone facilitated the pollen transport upslope to the subalpine area. By that time, Abies finally established in the vegetation cover of the Northwestern Rila Mountain after 8300-8200 cal. yrs. ВР. Even more, the short-term peak for Abies pollen curve, registered just before 9900 cal. yrs. ВР (Fig. 6) and the abundance of Polypodiaceae spores, can be viewed as a response to a more humid climate.
The second stage in the vegetation development, which broadly coincided with the Holocene climatic optimum, was characterized by important dynamic changes in the forest composition and its altitudinal zonation after 8000/7900 cal. yrs. BP. Over c. 2000 years the ecological conditions favored the vertical migration of the conifers (pollen zones LT-5, LR-5 and LSR-5; Fig. 7), particularly for Abies from lower altitudes and Pinuspeuce. The pioneer forests of Betula, and partly those of the mesophilous deciduous trees (Quercetum mixtum) and Corylus, gave way to Pinussylvestris, Pinuspeuce and Abies. Stomata of Pinus sp. in the fossil record of Lake Ribno indicate local presence of pines at this altitude, most probably Pinusmugo. Carpinusbetulus also slightly increased in the transitional zone between the deciduous and coniferous forests, together with the continuous, though still restricted appearance of Fagus stands. In the coniferous belt, or above it on rocky places, groups of birch were preserved as proved by the find of Betula fruits in the sediments of Lake Sedmo Rilsko, radiocarbon dated at 7400 cal. yrs. BP (Table 3). The formation of a coniferous belt presumes a climate shift towards cooler summers and warmer winters with increase in air and soil humidity in the Northern Mediterranean during the second half of the Atlantic period (Cheddadi et al., 1997), in contrast to a warming trend in Northern Europe (Davis et al., 2003). The appearance of Hedera pollen in the fossil record confirms this assumption.
The dynamic changes in the vegetation cover manifested after 5800 cal. yrs. BP (pollen zones LT-6, LR-6 and LSR-6; Fig. 7) lasted for 2400 years. Some increase of Pinuspeuce, Pinussylvestris and Pinusmugo was recorded, as well as the commencement of the gradual decline of Abies after its maximal spread at 4730 cal. yrs. BP. This transformation coincided with the regular, though restricted occurrence of Piceaabies in the study area. By that time the final establishment and the first signs for a wider distribution of Fagus in the Northwestern Rila Mountain were recorded. The spread of beech has begun rather late, after 4500 cal. yrs. BP, although its immigration from lower altitudes hadstarted earlier c. 7800 cal. yrs. BP. Beech formed pure or mixed woodstands either with Abiesalba or with Carpinusbetulus predominantly on northern slopes. Several alternatives alone, i.e. anthropogenic impact, climate change, deterioration of soil conditions or their complex interaction could be proposed to explain the establishment and subsequent expansion of Fagus in the mountains of the Balkans, Bulgaria included (Bennet, Willis, 1995; Bradshaw, Sykes, 2014). The climate change has been according to Huntley et al. (1989) the primary factor controlling Holocene migrations and abundance changes of Fagus in Europe and North America. At least in the lower mountain ranges of Southwestern Bulgaria the spread of Fagus on the place of the coniferous Pinus-Abies communities was favored by the anthropogenic activities (Tonkov, 2007; Marinova et al., 2012).
The first indications of human interference are visible in the pollen diagrams c. 3700 cal. yrs. BP when pollen of Cerealia-type together with the continuous presence of anthropogenic indicators such as Plantagolanceolata and Rumex appeared, accompanied by a decline for Abies. The archaeological information points to a rise in the number of the Late Bronze Age settlements (3400-3200 cal. yrs. BP) in the foothills of the mountains surrounding the Struma valley, and an intensification of the human activity, including deforestation (Marinova et al., 2012).
After 3400 cal. yrs. ВР Piceaabies started to invade areas in the coniferous belt, reaching the first expansion maximum c. 2700 cal. yrs. BP (pollen zones LT-7, LR-7 and LSR-7). This change in the vegetation cover was basically climate driven as a shift to lower average temperatures and an increase in precipitation that has occurred in the Northern Hemisphere. Concurrently, in the pollen record of Lake Sedmo Rilsko, the rise of Piceaabies and the tendency of a decline for Abies coincided with the appearance of pollen of anthropogenic indicators. The vegetation history in the study area since c. 2700 cal. yrs. BP years was characterized by an intensification of the human interference in all vegetation belts. At many places the upper timber-line was artificially lowered in order to extend pasture land. Even at high altitudes the find of cereal pollen from Triticum-type, Cerealia-type, and of Juglans, points to well-developed agriculture and cultivation of walnut in the foothills of the mountain, whereas pollen of Rumex, Plantagolanceolata, Scleranthus is indicative of livestock-grazing in the mountain meadows.
The pollen record from Lake Skakavitsa presents in more details the changes in the vegetation over the last 3800 years. Until 3000 cal. yrs. BP (pollen zone Sk-1; Fig. 15) the coniferous forests composed of Pinussylvestris, Abiesalba, Pinuspeuce with some Piceaabies dominated. Isolated stands of Fagus were distributed at lower elevations and below them mixed oak forests with Tilia, Ulmus, Carpinus, and Corylus were found on open terrains. Around the lake were growing stands of Pinusmugo and Juniperus. The PAR of tree taxa supports this reconstruction, the wider presence of fir until 3000 cal. yrs. BP and the low participation of spruce in particular (Fig. 16). For the time interval 3000-3800 cal. yrs. BP almost no indications for human presence and activities are recorded.
After 3000 cal. yrs. BP a couple of important changes in the forest composition are established in the pollen diagram from Lake Skakavitsa. Spruce started to invade areas in the coniferous belt and gained its first maximum c. 2500 cal. yrs. BP (pollen zone Sk-2). A similar behavior of beech at lower elevations led to its gradual enlargement after 2000 cal. yrs. BP. This period marks an intensification of the human interference in all vegetation belts. Even at high altitudes, like in the other studied lakes from the near-by cirque of the Seven Rila Lakes, the find of pollen from Cerealia-type and Juglans pointed to human activities. On the other hand, pollen of Juniperus, Rumex, Taraxacum-type, Plantago, Chenopodiaceae, Scleranthus was indicative of livestock-grazing in the mountain meadows. The higher influx values of deciduous tree taxa (Quercus, Carpinus, Corylus) could be explained by an easier air-transport upslope from lower elevations (Fig. 16). The final enlargement of Piceaabies and Fagus was reached in medieval time between 1600 and 700 cal. yrs. BP. Subsequently, both trees partly declined, whilst larger areas were occupied by pines, mostly Pinusmugo in the subalpine belt and Pinussylvestris.
The vegetation development over the last 2000 years at altitudes of 1300-1400 m is traced from the sediment archive of Lake Panichishte. The pollen and plant macrofossil records reveal that for the time interval 1900-1200 cal. yrs. BP or 50-750 AD (Figs 18, 19 and 21) the coniferous forests dominated by Pinussylvestris and Abiesalba, with some Pinuspeuce and few Piceaabies, were distributed around the lake. Monodominant plant communities of beech, or mixed in some places with fir and pines, also existed in the nearby vicinity. This reconstruction is proved by the find of female cones and needles from Abiesalba, needles and seeds from Pinussylvestris and leaf bud-scales from Fagussylvatica. The deciduous forests were composed of various oak species with Carpinusbetulus, Carpinusorientalis, Tilia and Corylus on more open areas. The herb communities consisted of Poaceae, Artemisia, Chenopodiaceae, Cichoriaceae, Achillea, Ranunculus, Brassicaceae species. The regular presence of anthropogenic pollen indicators such as Plantagolanceolata, Polygonumaviculare, Rumex, Cerealia-type, Secale, Triticum-type, though in low quantities, testifies for livestock-grazing in the meadows and cereal cultivation in the foothills of the mountain.
After 1200 cal. yrs. BP or 750 AD changes are recorded in the composition of the forests around the lake. Part of them were probably destroyed c. 1100 AD and, subsequently, the open areas were colonized by Betula and various herbs. In the entire Core P-2 (Fig. 18) subfossil fruits from Betulapendula are quite common with a maximal presence shortly before 700 AD. The high quantities of charcoal fragments presumes the occurrence of natural or human induced forest fires (Fig. 21). Also, Piceaabies and partly Pinuspeuce started gradually to expand.
In the course of several centuries (1400-1700 AD) the share of Abiesalba and Fagussylvatica considerably declined, caused mainly by an increase of the human impact and the invasion of Piceaabies. Spruce has benefited from the optimal ecological conditions for its growth in the forest zone between 1600 and 1300 m, concurrent with the duration of the Little Ice Age (1550-1850 AD) (Grove, 1988), and obviously being climatically influenced. The herb communities composed of various Poaceae, Artemisia, Achillea, Cichoriaceae, Ranunculus, Brassicaceae species, as well as Rumex, Plantagoaviculare and Juniperus occupied vast areas, thus pointing to intense seasonal livestock-grazing. The abundance of anthropogenic pollen (Triticum-type, Secale) confirms the cultivation of cereals.
The last three centuries witness the establishment of the present-day appearance of the forest cover around Lake Panichishte which is dominated by Pinussylvestris and Piceaabies, with an admixture of Abiesalba. The distribution of beech was reduced which can be explained by competition with the conifers, the insufficient air humidity and the soil structure. The pollen records reflect also a decline of the oak forests, quite probably as a result of their heavy exploitation for various purposes by the local population.
3.4 Central Rila Mountain – Study sitesLake Manastirsko 2 (site 6)
The lake is situated at 2326 m (42°07’46.78”N, 23°24’42.16”E) in the subalpine belt. It is 75 m long, 50 m wide, with a surface area of 0.2 ha and a maximum water depth of 2 m. The shores of the lake are flat and marshy, surrounded by sparse groups of Pinusmugo and Juniperussibirica among herb vegetation. The inlet brings water from a small upper lake and the outlet drains into Vodniza river (Ivanov, 1964) (Figs 3 and 23).
A976092D-ED12-5A3B-8BED-8683A1A32FF3
A view of Lake Manastirsko 2 (Photo: S. Tonkov).
https://binary.pensoft.net/fig/1672871
<italic>Coring, lithology and radiocarbon dating</italic>
A sediment core 415 cm long was obtained from the peaty southeastern shore with Dachnowsky hand-coring equipment. The lithology of the sediments is: 0-120 cm peat with sand, 120-385 cm peaty gyttja, 385-415 cm light-green gyttja. The radiocarbon age of 12 bulk sediment samples was determined and the results are shown in Table 6. The age of the sediment core is estimated at c. 13700 cal. yrs. BP (Tonkov et al., 2016).
Radiocarbon dates from Lake Manastirsko 2.
Lab. code
Depth (cm)
14C age (BP)
14C age cal. BP, ±2σ (mid-point)
Material dated
Ua-47271
26-28
1245±75
980-1300 (1140)
peat
Ua-49249
36-38
1517±31
1330-1530 (1430)
peat
Ua-47272
80-82
1915±38
1730-1950 (1840)
peat
Ua-48421
130-132
2703±41
2750-2880 (2815)
peaty gyttja
Ua-47273
180-182
3380±42
3480-3730 (3605)
peaty gyttja
Ua-48422
240-242
5858±47
6540-6790 (6665)
peaty gyttja
Ua-47274
280-282
7680±93
8310-8660 (8485)
peaty gyttja
Ua-47275
320-322
8972±106
9650-10400 (10025)
peaty gyttja
Ua-47423
360-362
9732±75
11060-11270 (11165)
peaty gyttja
Ua-49250
388-390
10380±85
11950-12550 (12250)
gyttja
Ua-47276
405-407
11209±168
12700-13400 (13050)
gyttja
Ua-49251
413-415
11796±174
13250-14050 (13650)
gyttja
<italic>Pollen analysis</italic>
Pollen analysis was conducted at 5 cm (2.5 cm for the lateglacial section) interval and a percentage pollen diagram is constructed (Fig. 24). Pollen accumulation rates (PAR) for the major tree/shrub and herb taxa are also calculated (Fig. 25). Fossil stomata were occasionally found on the pollen slides from several sample depths and their presence (*) is indicated on the pollen diagram. All stomata were identified as Pinus sp. Five local pollen assemblage zones (LPAZs) are recognized (LM-1 to LM-5) (Figs 24 and 7). Brief descriptions are as follows:
Pollen accumulation rates (PAR; pollen grains cm-2 yr-1) for the main tree/shrub and herb taxa from Lake Manastirsko 2 plotted against age in cal. yrs. BP.
https://binary.pensoft.net/fig/1672874
LPAZ LM-1 (415-378 cm, Artemisia-Chenopodiaceae-Pinus-Poaceae) (13700-11600 cal. yrs. BP).
The total tree pollen curve varies between 20% and 45% with two peaks of 55% (levels 415 cm and 405 cm). The main constituent is Pinusdiploxylon-type 10-30%, accompanied by Pinuspeuce up to 10%, Betula 5-10%, Juniperus, Quercus, Tilia, Ulmus, Corylus and Alnus, each up to 5%, and some Ephedra (distachya-type and fragilis-type). A short-term rise of Abies pollen with 5% is also recorded. Herb pollen is represented by Artemisia 15-40%, Chenopodiaceae up to 18%, Poaceae up to 15%, Achillea-type up to 5%, Cichoriaceae 5-8%, Galium-type, Rumex, Cirsium-type, Apiaceae, Brassicaceae, Dianthus-type, etc. The PAR of trees and herbs is rather low, c. 500 grains cm-2 yr-1 for each group. Tree pollen influxes are contributed mainly by Pinusdiploxylon-type with 150-250 grains.
LPAZ LM-2 (378-267 cm, Betula-Quercetum mixtum-Corylus-Pinus) (11600-7900 cal. yrs. BP)
The quantity of tree pollen increases from 40% to 75%, due to Pinusdiploxylon-type 20%, Pinuspeuce 5%, Corylus up to 10%, Betula 5-8%, Quercusrobur-type up to 10%, Tilia 5-7%, Quercuscerris-type 5%, Alnus, Ulmus and Tilia. Subsequently, Corylus starts to dominate with 15-25%, together with Betula up to 20%, Quercusrobur-type up to 15% and Quercuscerris-type 5%. The continuous pollen curve of Abiesappears and reaches 7%. Pollen grains of Fagus and Picea are regularly determined. The herb pollen taxa are represented by Poaceae 8-15%, Artemisia 5-8%, Cichoriaceae 5-10%, Chenopodiaceae 5%, Rumex 5-7%, Ranunculus-type, Brassicaceae, Apiaceae and Galium-type each with 3-5%. The total PAR of tree taxa increases gradually from c. 500 to nearly 2000 grains cm-2 yr-1, contributed significantly by Pinusdiploxylon-type 500-1000, Betula up to 300, Corylus 400-450 and Quercusrobur-type up to 200.
LPAZ LM-3 (267-220 cm, Pinus-Abies) (7900-5600 cal. yrs. BP)
The pollen curves of Abies, Pinusdiploxylon-type and Pinuspeuce rise up to 25%, 50-60% and 15%, respectively. Pollen of deciduous trees from Betula, Quercusrobur-type, Quercuscerris-type, Corylus, Tilia and Ulmus quickly declines. A continuous presence of Fagus and Picea, though with low frequencies, is recorded. Changes in the participation of the herb pollen taxa are not established, except for a decline of Poaceae below 5%. The PAR for Pinusdiploxylon-type and particularly for Pinuspeuce and Abies doubled compared to the previous zone.
LPAZ LM-4 (220-167 cm, Abies-Pinus-Fagus) (5600-3400 cal. yrs. BP)
The total tree pollen curve dominates with 80-90%, attributed to Pinusdiploxylon-type 40-60%, maximal frequencies for Abies 25-30%, Pinuspeuce 10-20%, Fagus and Picea each with 3-5%. Continuous pollen curves for Betula, Quercusrobur-type and Alnus are recorded. The most frequent herb pollen taxa are Poaceae 5%, Artemisia, Cichoriaceae, Rumex, Cirsium-type, Ranunculus-type, Brassicaceae, etc. The PAR for the main coniferous species starts sharply to increase, reaching maximal values: Pinusdiploxylon-type 3000 grains cm-2 yr-1, Pinuspeuce 1000 and Abies 1250.
LPAZ LM-5 (167-0 cm, Pinus-Picea-Abies-Fagus) (3400 cal. yrs. BP-until present)
Pollen of Picea continues to increase and reaches 10-15%, while Abies declines to 10-15%. High values are established for Pinusdiploxylon-type 60-65% and Pinuspeuce 10-15%. A slight increase for Betula, Corylus, Alnus and Fagus is recorded. Pollen of Juglans is occasionally found. A higher diversity of herb pollen taxa is present, in particular the appearance of anthropogenic indicators like Secale, Hordeum-type and Plantagolanceolata, accompanied by an increase for Poaceae and Cichoriaceae pollen. A secondary rise of the pollen curve of Cichoriaceae with 5-8% is established, together with Poaceae, Achillea-type, Artemisia, Scleranthus, Brassicaceae, etc. In the uppermost samples the total PAR of trees and shrubs substantially decreases, particularly noticeable for Pinusdiploxylon-type, Picea, Abies and Fagus.
Peat bog Vodniza (site 7)
This peat bog is a former lake located in the upper part of the coniferous belt near the timber-line at 2113 m (42°08’13.31”N, 23°25’23.75”E), below c. 200 m in altitude from Lake Manastirsko 2 (Fig. 3). The site has an elongated shape 90 m long and 40 m wide. It is formed in a depression with a steep and stony southwestern slope, surrounded by groups of Pinusmugo, Pinuspeuce, Piceaabies and Juniperussibirica. A small brook runs through the peat bog and drains into Vodniza river. The bog surface and its peripheral parts are overgrown by spots of Sphagnum spp., Carexnigra, Carexrostrata, Deschampsiacespitosa, Phleumalpinum, Eriophorumangustifolium, Eriophorumlatifolium, Calthalaeta, Trolliuseuropaeus, Geumcoccineum, Geumbulgaricum, Sileneroemeri, Veratrumlobelianum, Bartsiaalpina, Rumexalpinus, Bistortavivipara, Campanulasparsa, Plantagogentianoides, Senecionemorensis, Tripleurospermumcaucasicum, etc. (Tonkov et al., 2018, 2022) (Fig. 26).
8C15D4F1-A05B-5B40-B7BE-659982D6CFD9
A view of Peat bog Vodniza (Photo: S. Tonkov).
https://binary.pensoft.net/fig/1672875
<italic>Coring, lithology and radiocarbon dating</italic>
A sediment core 640 cm long was obtained from the central part of the peat bog with Dachnowsky hand-coring equipment. The lithology of the sediments is: 0-215 cm sedge peat with plant fragments, 215-520 cm peaty gyttja, 520-595 cm clayish gyttja and 595-640 cm silty clay. The radiocarbon age of 11 bulk sediment samples was determined and the results are shown in Table 7. The age of the core is estimated at c. 17500 cal. yrs. BP. (Tonkov et al., 2018, 2022).
Radiocarbon dates from Peat bog Vodniza.
Lab. code
Depth (cm)
14C age (BP)
14C age cal. BP, ±2σ (mid-point)
Material dated
Ua-54136
71-73
877±26
720-910
peat
(815)
Ua-54137
151-153
1561±27
1390-1530 (1460)
peat
Ua-55775
214-216
2387±31
2340-2680 (2510)
peaty gyttja
Ua-54138
253-255
3168±28
3350-3460 (3405)
peaty gyttja
Ua-54139
333-335
5196±30
5900-6000 (5950)
peaty gyttja
Ua-55011
384-386
6756±35
7570-7670 (7620)
peaty gyttja
Ua-47275
441-443
7572±34
8340-8430 (8385)
peaty gyttja
Ua-54141
487-489
8501±35
9460-9540 (9500)
peaty gyttja
Poz-37534
505
8970±50
10240-9900 (10070)
peaty gyttja
Poz-37537
523-525
11200±50
13240-13000 (13120)
clayish gyttja
Poz-37535
601-604
14350±90
17850-17140 (17500)
silty clay
<italic>Pollen analysis</italic>
Pollen analysis was conducted at 5-10 cm interval. The lowermost 35 cm contain no pollen. A percentage pollen diagram is constructed (Fig. 27). A separate pollen diagram including the termination of the Pleniglacial and the Lateglacial is also presented (Fig. 27a). Pollen accumulation rates (PAR) for the major tree/shrub and herb taxa are calculated (Fig. 28). On the pollen diagram eight local pollen assemblage zones (LPAZs) can be recognized (V-1 to V-8) (Figs 27 and 7). Brief descriptions are as follows:
Percentage pollen diagram of Peat bog Vodniza – Lateglacial section.
https://binary.pensoft.net/fig/1672878
LPAZ V-1 (605-553 cm, Artemisia-Chenopodiaceae-Poaceae) (~17500-14700 cal. yrs. BP)
The total herb pollen dominates with 85-75%, attributed to Artemisia 40-45%, Chenopodiaceae up to 30% and Poaceae up to 20%. A short-term rise of the tree pollen curve with 60% (level 575 cm) on the account mainly of Pinusdiploxylon-type 40% and Pinuspeuce 15% is registered. Single pollen grains of a number of coniferous (Abies, Picea, Juniperus) and deciduous (Betula, Quercus, Ulmus, Tilia, Fagus) trees are also determined. The total PAR of tree taxa is rather low, below 200 grains cm-2 yr-1, with an exception of 500 (level 575 cm), contributed by Pinusdiploxylon-type 400, and less than 50 for Betula and Juniperus each. The total PAR of herb taxa reaches 1000 grains cm-2 yr-1, represented by Artemisia 500, Chenopodiaceae 250 and Poaceae 240.
LPAZ V-2 (553-528 cm, Pinus-Betula-Artemisia) (14700–13200 cal. yrs. BP)
In this zone tree pollen dominates with 60-55% in contrast to the previous zone, represented by Pinusdiploxylon-type up to 50%, Pinuspeuce 10%, Betula 5%, minor percentages of Quercuscerris-type, Corylus, etc. The total presence of herb pollen declines to 40%, contributed by Artemisia 20-30%, Chenopodiaceae up to 15% and Poaceae 15-10%. A slight increase in the participation of Cyperaceae pollen and Polypodiaceae spores is established. The total PAR of tree taxa is c. 500 grains cm-2 yr-1, contributed by Pinusdiploxylon-type 400, and 50 for Betula. The total PAR of herb taxa declines to 500-700 as shown by Artemisia 200-250, Chenopodiaceae 50-100 and Poaceae 50-100.
LPAZ V-3 (526-517 cm, Artemisia-Chenopodiaceae-Poaceae) (13200-11700 cal. yrs. BP)
The total herb pollen dominates again with 75-50%, represented by Artemisia up to 42%, Chenopodiaceae and Poaceae up to 18-20% each, accompanied by a great variety of other herbs (Achillea-type, Cirsium-type, Centaurea, Thalictrum, Rumex, etc.). Tree pollen sticks to low values of c. 25% but rises to 50% at the transition to the next zone, attributed to Pinusdiploxylon-type 20%, Pinuspeuce 5%, Betula 10%. The PAR of all taxa is remarkably very low, i.e. for the tree taxa 40-50 grains cm-2 yr-1 and for the herb taxa 100-170.
LPAZ V-4 (517-425 cm, Betula-Pinus-Quercetum mixtum-Corylus) (11700-8150 cal. yrs. BP)
The tree pollen dominates with 80-95%, due to Betula up to 25%, Pinusdiploxylon-type 20-40%, Pinuspeuce 5-15%, Quercusrobur-type 10%, Quercuscerris-type 5-10%, Corylus 5-12%, Tilia 2-4%. Low pollen frequencies are established for Acer, Carpinusbetulus, Ulmus, Alnus, Fagus and Picea. The continuous pollen curve of Abies starts in this zone. The herb pollen taxa are represented by Poaceae 5-8%, Artemisia 3%, Cichoriaceae 2%, Rumex 2%, Ranunculus-type, Brassicaceae, Apiaceae, etc. Spores of Polypodiaceae do not exceed 5%. The total PAR of tree taxa increases from 1500 to 3000 grains cm-2 yr-1, contributed mainly by Pinusdiploxylon-type 1000, Betula 350-500, Quercus 200-400, Corylus up to 400.
LPAZ V-5 (425-315 cm, Pinus-Abies-Quercetum mixtum) (8150-5350 cal. yrs. BP)
The pollen curves of Pinuspeuce and Abies rise to 25% and 10%, respectively. The pollen frequency of Pinusdiploxylon-type is 40-45%. The presence of deciduous tree pollen from Betula, Quercuscerris-type, Quercusrobur-type, Corylus, Tilia and Ulmus begins to decline. Pollen of Fagus and Picea, although with rather low values, is regularly found. Pollen of Vitis, Humulus/Cannabis-type and Vaccinium-type is also recorded. Significant changes in the presence of the herb pollen taxa are not observed, except for a slight rise of Cichoriaceae and a reduction of Polypodiaceae spores. The total PAR of tree taxa quickly increases to 7500-9500 grains cm-2 yr-1 due to Pinusdiploxylon-type 4000-4500, Pinuspeuce 1500-2000, Corylus 800, and then declines to c. 4000. The relevant values for Abies reach 400-600.
LPAZ V-6 (315-255 cm, Pinus-Abies-Fagus) (5350-3450 cal. yrs. BP)
The presence of total tree pollen is 87-95%, attributed to Pinusdiploxylon-type 40-60%, maximal frequencies for Pinuspeuce 20-30%, Abies 10%, Quercusrobur-type and Fagus each up to 3-5%. Pollen of deciduous trees from Carpinusbetulus, Carpinusorientalis/Ostrya, Ulmus, Tilia is constantly present with low values. The most common herb pollen taxa are Poaceae 5%, Cichoriaceae, Chenopodiaceae, Ranunculus-type, Dianthus-type, Brassicaceae. The total PAR of tree taxa is between 3500 and 6000 grains cm-2 yr-1, contributed mainly by Pinusdiploxylon-type 2000-2500, Pinuspeuce 1000, Abies 450, Fagus 200.
LPAZ V-7 (255-85 cm, Pinus-Picea-Fagus-Abies) (3450-950 cal. yrs. BP)
The sharp increase of Picea pollen up to 10-15% is accompanied by a maximum for Fagus 10%. Pollen of Pinusdiploxylon-type, Pinuspeuce and partly Abies tends to decline. Minor values below 5% are recorded for pollen of Betula, Alnus, Corylus, Quercusrobur-type, Quercuscerris-type and Carpinusbetulus. Pollen of Juglans, Humulus/Cannabis-type and Vaccinium-type is occasionaly found. The total PAR of tree taxa is between 2500 and 4500 grains cm-2 yr-1. The values established for Picea are 400, Fagus 200-300 and Abies 200-600. The highest presence of Poaceae (up to 10% and PAR of 350), an increase for Cichoriaceae (PAR up to 900), Artemisia, Chenopodiaceae, Rumex, Brassicaceae is recorded. Pollen of Plantagolanceolata and Hordeum-type appears. The presence of Cyperaceae pollen and spores of Selaginellaselaginoides and Sphagnum is worth to be mentioned.
LPAZ V-8 (85-0 cm, Pinus-Picea-Abies) (950 cal. yrs. BP-until present)
The quantity of total tree pollen declines to 70%, attributed mainly to Abies, Picea, Fagus, Pinuspeuce, Quercus and Betula. Pollen of Pinusdiploxylon-type reaches a maximum of 60%. The total PAR of tree taxa is similar to the previous zone, with some increase for Pinusdiploxylon-type up to 2000 grains cm-2 yr-1, a decline for Abies and deciduous taxa. The herb pollen is characterized by higher percentages of Cichoriaceae (PAR up to 900), Apiaceae, Chenopodiaceae, Plantagolanceolata.
Fossil stomata from needles of conifers were identified and counted together with pollen. Their presence in absolute numbers is indicated on the pollen diagram (Fig. 27). The taxonomic identification was aimed particularly in attempt to distinguish between Pinusmugo/sylvestris and Pinuspeuce. Fossil stomata were regularly found on the pollen slides in the interval 480-210 cm (9300-2400 cal. yrs. BP), usually in the form of detached individuals, and rarely in small groups joined by fragmentary epidermal tissue. The number of stomata is below 10 per sample with several exceptions. It is likely that most of the stomata recovered in gyttja sediment cores are released during the disintegration of leaves in shallow peripheral parts and then probably resuspended and distributed in a manner similar to pollen (MacDonald, 2001). The taxonomic resolution usually reaches only the genus level, which is comparable to pollen, but lower than for macrofossils. The taxonomic identification of the fossil stomata revealed that they originated from three genera: Pinus, Juniperus and Picea (Fig. 29). Most numerous are the fossil stomata from Juniperus sp. (9300-2400 cal. yrs. BP), followed by those of Pinus sp. (Pinusmugo/sylvestris, Pinuspeuce) (8150-3150 cal. yrs. BP) and Piceaabies (3100-2400 cal. yrs. BP). Fossil stomata of spruce appear in the sediment record after 3100 cal. yrs. BP, which is in good conformity with the quick rise of Picea pollen curve c. 3300 cal. yrs. BP (Fig. 27). The attempts to distinguish between fossil stomata from Pinusmugo/sylvestris and Pinuspeuce (Diploxylon-type from Haploxylon-type) on the basis of morphological and size differences were not successful, mainly due to their low number and the impossibility to apply measurement statistics. This observation was recently supported by Finsinger, Tinner (2020) in their detailed study of stomata of conifers. The authors noted that the stomata of European species of the Pinaceae family analysed bear genus-specific features which confirmed earlier studies by Trautmann (1953) who claimed for instance that among species of Pinus sp. the stomata morphologies were not distinguishable with simple visual observations of stomata features. Therefore, it is accepted that in our case fossil Pinus stomata originate from all three pine species (Pinusmugo, Pinussylvestris and Pinuspeuce) which grow today in the study area.
C4FFC318-FA85-5773-9527-624B833603D4
Pollen accumulation rates (PAR; pollen grains cm-2 yr-1) for the main tree/shrub and herb taxa from Peat bog Vodniza plotted against age in cal. yrs. BP.
Photos of fossil stomata from Peat bog Vodniza (scale bar = 30 μm). A. Piceaabies. B. Pinus sp. C. Juniperus sp. (after Tonkov et al., 2018).
https://binary.pensoft.net/fig/1672880Lakes Ostrezki (sites 8 and 9)
The group of Lakes Ostrezki comprises several lakes with permanent water surface and half a dozen smaller ones that dry up in summer. The group is located in the subalpine belt above the present tree-line on the western slope of a large cirque (Fig. 3). Lake Ostrezko 2 (site 8) is located at 2320 m (42°07’14.18”N, 23°29’11.33”E) and has an elliptic shape with peaty shores and an area of about 0.15 ha. The water depth is 1.5 m (Fig. 30). Lake Ostrezko 3 (site 9) is located at 2340 m (42°07’16.24”N, 23°29’13.53”E) and has a circular shape with an area of about 0.1 ha and water depth of 1.7 m (Fig. 31). The distance between both lakes is 60 m. The lakes are surrounded by groups of Pinusmugo and Juniperussibirica and herb vegetation composed of Nardusstricta, Poaalpina, Deschampsiacespitosa, Carexnigra, Carexechinata, Campanulaalpina, Geumcoccineum, Geummontanum, Ranunculusmontanus, Potentillaternata, Dianthusmicrolepis, Plantagogentianoides, Primuladeorum, Gentianapyrenaica, etc. (Tonkov, Marinova, 2005).
https://binary.pensoft.net/fig/1672882
<italic>Coring, lithology and radiocarbon dating</italic>
The core from Lake Ostrezko 2 was recovered from the northern peaty shore. The core is 200 cm long and the lithology of the sediments is: 0-25 cm Sphagnum peat, 25-200 cm gyttja. The core from Lake Ostrezko 3 was recovered from the southern periphery of the lake at water depth of 0.7 m. The core is 180 cm long and the sediment is gyttja. The equipment used was Dachnowsky hand-coring. The radiocarbon age of 5 bulk sediment samples was determined and the results are shown in Table 8.
Radiocarbon dates from Lakes Ostrezki.
Lab. code
Depth (cm)
14C age (BP)
14C age cal. BP, ±2σ (mid-point)
Material dated
Ostrezko 2
B-6101
53-67
1290±40
1300-1080 (1190)
gyttja
B-6617
95-105
2720±40
2920-2750 (2835)
gyttja
B-6099
146-154
3510±40
3890-3640 (3765)
gyttja
B-6098
175-185
4830±40
5650-5470 (5560)
gyttja
Ostrezko 3
J-361
150-156
5700±35
6620-6400 (6510)
gyttja
<italic>Pollen analysis</italic>
The cores were sampled at 5-10 cm intervals and two percentage pollen diagrams are constructed (Figs 32 and 33). The palynostratigraphical correlation of the cores is feasible due to the similarities in the behaviour of the main pollen curves and the application of a depth/age model constructed for Lake Ostrezko 2. As a result, four local pollen assemblage zones (LPAZs) are recognized (LOS-1 to LOS-4) and the oldest LPAZ LOS-1 is present only in the pollen diagram from Lake Ostrezko 3 (Figs 33 and 7). Brief descriptions are as follows:
LPAZ LOS-1 Lake Ostrezko 3 (180-155 cm, Pinus-Abies-Corylus) (~ 6760-6500 cal. yrs. BP)
Pollen of Pinusdiploxylon-type dominates with 40-50%, accompanied by Abies 5-10%, Pinuspeuce 4% and pollen of Corylus 15-25%, Betula, Tilia, Ulmus and Quercus. Single pollen grains of Picea and Fagus are recorded. The herb pollen taxa are represented by Poaceae 5-10%, Cichoriaceae, Artemisia, Centaurea, Dianthus-type, etc.
LPAZ LOS-2 Lake Ostrezko 3 (155-117 cm), Lake Ostrezko 2 (200-145 cm) (Abies-Pinus) (6500-3670 cal. yrs. BP)
Pollen of Abies rises to 30% and Pinusdiploxylon-type reaches 40-60%. The pollen curve of Fagusappears in this zone. Among the herb pollen taxa are determined Poaceae, Achillea-type, Cirsium-type, Apiaceae, etc.
LPAZ LOS-3 Lake Ostrezko 3 (117-27 cm), Lake Ostrezko 2 (145-55 cm) (Pinus-Picea-Abies) (3670-1100 cal. yrs. BP)
The dominant pollen type is Pinusdiploxylon with 50%. The pollen curve of Piceaappears and increases to 7%. Pollen of Abies tends to decline and a slight increase for Fagus is established. The presence of Corylus pollen is insignificant. Alongside with the great variety of herb pollen taxa, the continuous presence of anthropogenic pollen indicators such as Plantagolanceolata, Plantagomajor/media-type, Scleranthus, Urtica and Galium-type begins.
LPAZ LOS-4 Lake Ostrezko 3 (27-0 cm), Lake Ostrezko 2 (55-5 cm) (Pinus-Picea-Fagus) (1100 cal. yrs. BP-until present)
Pollen of Pinusdiploxylon-type increases to 60-80%, as well as pollen of Picea and Fagus each with 10%. The pollen curve of Abies declines to 8%. Pollen of Juglans is also found. Various herb pollen taxa are also determined, among them the share of the anthropogenic pollen indicators such as Plantagolanceolata, Rumex, Artemisia, Cichoriaceae, Secale and Hordeum-type increases.
<italic>Plant macrofossil analysis</italic>
The samples for plant macrofossil analysis were taken at every 10-20 cm and studied at magnification 10-40×. Macrofossils such as fruits and seeds are presented in absolute numbers per 20 ml (Lake Ostrezko 2) and per 40 ml (Lake Ostrezko 3). The abundance of wood fragments and remains of vegetative parts (stems, leaves, etc.) is shown on a relative scale by black dots (Figs 34 and 35). The analysis is focused on the core from Lake Ostrezko 2 which is bound to a radiocarbon chronology. The results from the macrofossil determination allow to distinguish three local macrofossil assemblage zones (LMAZs) and their description (MOS-1 to MOS-3) is briefly as follows:
LMAZ MOS-1: Lake Ostrezko 2 (200-150 cm), Lake Ostrezko 3 (180-90 cm) (~ 6760-3760 cal. yrs. BP)
The fossil record contains needles, seeds, female cones of Pinusmugo, Pinuspeuce, needles of Pinussylvestris and wood of Pinus sp., fruits of Alnusviridis, seeds and fruits of various herbs such as Dianthus, Silene, Thymus, etc. Charcoal particles are also found.
LMAZ MOS-2: Lake Ostrezko 2 (150-50 cm), Lake Ostrezko 3 (90-33 cm) (3760-1000 cal. yrs. BP)
Abundant needles of Pinusmugo, Pinussylvestris and Juniperussibirica are present. The first records of Piceaabies and Abiesalba needles are established. Seeds of Cardamine, Cirsium, Doronicum, etc. are determined and remains of mosses as well.
LMAZ MOS-3: Lake Ostrezko 2 (50-5 cm), Lake Ostrezko 3 (33-10 cm) (1100 cal. yrs. BP-until present)
The plant macrofoossil record is rather poor, represented by sporadic finds of needles from Pinusmugo, Pinussylvestris, Piceaabies, Juniperussibirica; fruits of sedges and vegetative parts of mosses (Sphagnum, Drepanocladus).
Lake Malko Smradlivo (site 10)
The lake is located at 2300 m (42°07’24.30”N, 23°28’14.40”E) in the subalpine vegetation belt above the present tree-line formed by Pinuspeuce with an admixture of Piceaabies and Pinussylvestris (Fig. 3). It drains into Lake Smradlivo which is the largest mountain lake on the Balkans. The open water surface of the lake is c. 0.5 ha and the water depth is 1-1.3 m. The shores of the lake are flat and peaty. The surrounding slopes are gentle, only the western slope is steep and stony, covered by stands of Pinusmugo and herb vegetation composed of Nardusstricta, Poaalpina, Deschampsiacespitosa, Carexnigra, Carexechinata, Geumcoccineum, Geummontanum, Ranunculusmontanus, Dianthusmicrolepis, Plantagogentianoides, etc. (To nkov, 2005) (Fig. 36)
FB137B9A-6710-5C5B-9C1C-F105A51609DC
A view of Lake Malko Smradlivo (Photo: S. Tonkov).
https://binary.pensoft.net/fig/1672888
<italic>Coring and lithology</italic>
The core for pollen analysis was taken with Dachnowsky hand-operated equipment from the northern peaty shore. The core length is 140 cm and the sediment is peaty gyttja overlain in the uppermost 30 cm by undecomposed Sphagnum peat.
<italic>Pollen analysis</italic>
The core was sampled at 10 cm interval and a percentage pollen diagram is constructed (Fig. 37) On the pollen diagram two local pollen assemblage zones (LPAZs) are recognized (Smr-1 and Smr-2) based on the changes in the behaviour of the pollen curves of Pinusdiploxylon-type, Pinuspeuce, Picea and Abies. Due to the lack of radiocarbon dates the zones are biostratigraphically compared with the corresponding intervals of the radiocarbon dated core from the nearby Lake Ostrezko 2 (Tonkov, Marinova, 2005). A relatively young age of the core is suggested. A brief description of the LPAZs is as follows:
F36B729D-B673-51B0-A3F2-3709FBC63D3B
Percentage pollen diagram of Lake Malko Smradlivo.
https://binary.pensoft.net/fig/1672889
LPAZ Smr-1 (140-65 cm)
Pollen of Pinusdiploxylon-type prevails with c. 40% and a decrease to 17% (level 100 cm) is observed. Pollen of Pinuspeuce increases from 10% to 20%. Abies is comparatively well represented with up to 10%, together with Fagus 5-7% and Picea 5%. Pollen of Quercusrobur-type and Quercuscerris-type reaches 3-5%. Low percentages are recorded for Corylus, Carpinus, Acer and Humulus/Cannabis pollen. The highest pollen frequences of Poaceae up to 20% and Artemisia up to 12% are established in this zone. Pollen of Cichoriaceae, Ranunculus and Rumex is also found. Quite common are pollen grains of Secale and spores of Polypodiaceae.
LPAZ Smr-2 (65-0 cm)
An increase in the presence of Pinusdiploxylon-type up to 45-50% is registered, together with an increase of Pinuspeuce reaching 30% in the uppermost sample. Lower pollen percentages are recorded for Abies, Fagus and for nearly all deciduous trees (Carpinus, Acer, Corylus, Quercus, Alnus). Pollen of Picea is c. 10%. Quite common are pollen grains of Juniperus. A reduction in the presence of the herb pollen taxa is also observed which can be explained with the aeration of the soft undecomposed Sphagnum peat, thus creating unfavorable conditions for the preservation of the pollen grains. The presence of Poaceae declines to 5-10%. The same tendency is recorded for Cichoriaceae, Ranunculus-type, Dianthus-type, Scleranthus, etc. Spores of Polypodiaceae are not so common unlike the abundance of Selaginellaselaginoides spores.
Lake Suho Ezero-RM (site 11)
This lake is one of the lowest located lakes in the mountain at 1900 m (42°09’57.61”N, 23°25’07.30”E) northeast from the Rila Monastery (Fig. 3). Its origin is most likely tectonic. The lake has an elongated shape with a length of 380 m and a maximum width of 70 m. The water surface area is 1.95 ha. It receives two tributaries from the north and one from the east. The lake has a visible outlet and often dries up completely at the end of summer (Ivanov, 1964) (Figs 38 and 38a). The slope that descends to the northern shore is steep and groups of Alnusviridis, single trees of Pinussylvestris, Betulapendula, Populustremula, Pinuspeuce and Piceaabies grow in the gullies. The coniferous forest around the southern and eastern shores is composed of Piceaabies with an admixture of Pinuspeuce and Pinussylvestris. The flat western shore is occupied by groups of Pinusmugo and Juniperussibirica. In the approaches to the lake from the Rilska river valley between 1500 and 1850 m are growing Abiesalba, Acerheldreihii, Acerpseudoplatanus, Sorbusaucuparia, Populustremula and Fagussylvatica. The herb communities on the open areas around the lake are composed of Festucavalida, Calamagrostisarundinacea, Anthoxanthumodoratum, Tripleurospermumcaucasicum, Geumcoccineum, Thalictrumaquilegifolium, Centaureanervosa, Campanulaalpina, etc. The highly ruderalized places are dominated by Rumex acetosella, Rumexalpinus, Cirsiumappendiculatum, Urticadioica, Veratrumalbum (Tonkov et al., 1998).
601B20A1-4ECA-5AF5-B820-670DF61AB271
A view of Lake Suho Ezero-RM with water (Photo D. Kozuharov).
A view of Lake Suho Ezero-RM without water (source: ranica.bg).
https://binary.pensoft.net/fig/1672891
<italic>Coring, lithology and radiocarbon dating</italic>
A core 320 cm long was obtained from the southwestern part with Dachnowsky hand-coring equipment when the lake was completely dried up (Fig. 38a). The lithological composition of the sediments shows an alternation of gyttja layers mixed with sand and sand layers. The thickness of these layers varies from 2 to 25 cm. There is no regularity in the distribution of the two main lithological units. One possible explanation for the formation of these layers might be the irregular drying of the lake and the deposition of coarse inorganic eroded material which contributes to the absence of a stable hydrological regime. The position of these layers is indicated on the pollen diagram. The radiocarbon age of 2 bulk sediment samples was determined and the results are shown in Table 9. The exact time when the sedimentation of the analyzed core has started is difficult to determine. It is obvious that the uppermost 140 cm were deposited during the last 1400 years and the pollen stratigraphy of the core indicates most probably a Subatlantic age.
Radiocarbon dates from Lake Suho Ezero-RM.
Lab. code
Depth (cm)
14C age (BP)
14C age cal. BP, ±2σ (mid-point)
Cal. AD (mid-point)
Material dated
LuA-4315
52-64
1290±100
1360-980 (1170)
590-970 (780)
gyttja with sand
LuA-4316
130-140
1470±110
1615-1170 (1400)
335-780 (550)
gyttja
<italic>Pollen analysis</italic>
The core was sampled each 5 cm or at longer/shorter intervals to avoid the sand layers. On the percentage pollen diagram (Fig. 39) four local pollen assemblage zones (LPAZs) can be distinguished (RM-1 to RM-4). Brief descriptions are as follows:
The participation of Pinusdiploxylon-type is 30-55%, Pinuspeuce 5-13%, Picea up to 18%, Fagus 5-7%, Betula and Alnus each with 5-7%, Abies 5%, and minimal values for Juniperus, Quercus, Tilia, Corylus and Carpinusbetulus. Pollen of Juglans is regularly found. The herb pollen taxa are rather diverse and present with low frequencies (except for Poaceae with 5-15%) such as Cichoriaceae, Achillea-type, Artemisia, Chenopodiaceae, Scleranthus, Rumex, Dianthus-type, etc.
LPAZ RM-2 (218-133 см, Pinus-Abies)
Pollen of Pinusdiploxylon-type with 60% dominates together with Pinuspeuce 18%. A maximal value of 16% is registered for Abies pollen. A slight increase to 12% is established for Quercusrobur-type and Corylus 4%, while Fagus, Alnus and Betula decrease. Among the herb pollen taxa should be mentioned Cichoriaceae, Plantagolanceolata, Scleranthus, Ranunculaceae, Thalictrum, Gentiana, Cerealia-type, Triticum-type, etc.
LPAZ RM-3 (133-53 см, Pinus-Picea-Fagus) (1400-1170 cal. yrs. BP)
Pollen of Pinusdiploxylon-type retains its dominant role with 35-55%. Picea and partly Fagus, Betula, Alnus, Juniperus increase again. Pollen of Abies decreases to 2-3%. The herb pollen taxa are rather diverse, represented by Poaceae 18%, Achillea-type, Plantagolanceolata, Rumex, Scleranthus, Secale, Ranunculus-type, Apiaceae, Brassicaceae, Caltha-type, etc.
LPAZ RM-4 (53-0 см, Picea-Pinus) (1170 cal. yrs. BP-until present)
The pollen curve of Picea reaches maximal values of 20-23% together with Pinuspeuce 8-12%. Pollen of Pinusdiploxylon-type declines to 30%. The herb pollen taxa are almost the same like in the previous zone with a more pronounced presence of Rumex, Cerealia-type, Secale and Triticum-type.
3.5 Vegetation history in the Central Rila MountainLateglacial
The oldest continuous pollen record from this part of the Rila Mountain originates from the Peat bog Vodniza and spans the last c. 17500 years. The lateglacial paleoenvironmental changes and vegetation dynamics are traced also from the pollen record of Lake Manastirsko 2 which dates back 14000 years. The pollen assemblages indicate stadial conditions at the termination of the Late Pleniglacial when the landscape at high- mid altitudes was dominated by herb communities composed of cold-resistant and heliophilous taxa belonging to Artemisia, Chenopodiaceae, Poaceae, Brassicaceae, Apiaceae, Achillea, Thalictrum, Dianthus, etc. (pollen zone V-1, Fig. 27a). Within this vegetation, isolated stands of Pinus (Pinusmugo, Pinussylvestris, Pinuspeuce), Betula and shrubland of Juniperus-Ephedra occurred. A short-term spread of Pinus, Betula, Abies and several deciduous trees (Quercus, Carpinus, Ulmus, Tilia), presumably in sheltered habitats at lower elevations, is interpreted as a consequence of a climate improvement at c. 16000 cal. yrs. BP.
The climate warming after c. 14700 cal. yrs. BP initiated afforestation with Pinus, Betula and Alnus. The “mountain-steppe” herb vegetation dominated by Artemisia, Chenopodiaceae and Poaceae was partially reduced. At lower altitudes deciduous trees (Quercus, Corylus, Tilia, Carpinusbetulus) spread from their local microrefugia where moisture and temperature were favorable for growth. The chronological framework of this time interval (pollen zone V-2, Fig. 27a; partly pollen zone LM-1, Fig. 24) is clearly defined and correlates well with the Bølling/Allerød interstadial complex. It is visible that the lateglacial interval at Lake Manastirsko 2 covers only the lowermost 37 cm of the sequence and due to the low time resolution, a clear distinction between the upper part of the Bölling/Alleröd interstadial complex and the Younger Dryas stadial is hardly possible.
Тhe pollen spectra after c. 13200 cal. yrs. BP indicate a reversal towards stadial conditions, manifested by an increase of Artemisia, Chenopodiaceae, Poaceae, and other herb taxa. A steep decrease in the abundance of tree pollen, particularly of Pinusdiploxylon-type, Pinuspeuce, and partly Betula and Quercus is observed (pollen zone V-3, Fig. 27a). This pollen zone can be correlated with the last cold phase of the Lateglacial, the Younger Dryas stadial, during which the “mountain-steppe” herb communities re-advanced at the expense of the tree vegetation which moved downslope.
The short-term rise of Abies, and the peak of the total tree pollen curve c. 12700 cal. yrs. BP (pollen zone LM-1, Fig. 24), can be interpreted as response to a signal of climate improvement which correlates with the GRIP δ18O curve indicating a warmer interval (GI-1a) (Dansgaard et al., 1993). At lower altitudes deciduous trees started gradually to spread from places where humidity and soil moisture were sufficient for their growth.
The low PAR of trees c. 500 grains cm-2 yr-1 throughout the Lateglacial (Figs 25 and 28), contributed mainly by Pinusdiploxylon-type, confirms the scarce, most likely isolated presence of pines (Pinusmugo/sylvestris). The abundance of Pinuspeuce and Betula can be considered as disparagingly low. Regarding the PAR of the main herbs, a steep decline in the values for both Artemisia and Chenopodiaceae is observed at 12700 cal. yrs. BP, and a gradual increase for the pollen influx of Poaceae at the transition to the Holocene (Fig. 25).
For the first time in Bulgaria the lateglacial record from Peat bog Vodniza was used for chironomid-inferred July temperature reconstruction (Tonkov et al., 2022). Details for more information on the reconstruction methods applied are found in Heiri et al. ( 2014). The temperature values plotted (Fig. 27a) indicate a gradual climate improvement during the Lateglacial. It started with an increase from 5°C to 8°C after 16000 cal. yrs. BP until c. 14700 cal. yrs. BP. During the Bølling/Allerød interstadial complex a couple of fluctuations around 8°C are recorded but c. 13700 cal. yrs. BP the temperature reached 10°C. This tendency was preserved during the Younger Dryas stadial and the transition to the Holocene marked a rise to 10-12°C.
Holocene
Comprehensive information on the Holocene vegetation dynamics is obtained from Peat bog Vodniza and Lake Manastirsko 2, while the paleoecological records from Lakes Ostrezki span the last 6700 years, and from Lake Suho Ezero-RM and Lake Malko Smradlivo the last c. 2500-2000 years.
The amelioration of the climate with an increase of temperatures at the onset of the Holocene resulted in quick afforestation and diminishing of the areas occupied by the “mountain steppe” herb vegetation dominated by Artemisia, Chenopodiaceae and other cold-resistant herbs. Initially, boreal forests of Betula with groups of pines (Pinusmugo, Pinussylvestris, Pinuspeuce) and some Juniperus, began to colonize areas at mid-high altitudes on barren soils during the time interval 11600-9800/9500 cal. yrs. BP (the lower parts of pollen zones LM-2 and V-4, Figs 24 and 27). The presence of pines in the near vicinity of Lake Manastirsko 2 and Peat bog Vodniza is justified by the first finds of fossil stomata at 11000-10000 and c. 9500 cal. yrs. BP, respectively. More likely, they derived from Pinusmugo. The participation of Juniperus in the early Holocene vegetation cover is confirmed by the continuous presence of fossil stomata since 9300 cal. yrs. BP in the sediments of Peat bog Vodniza (Fig. 27).
Meanwhile, the birch forests reached their maximal distribution c. 9500 cal. yrs. BP and the share of Pinus has gradually increased. The composition of the pollen assemblages indicates the beginning of widespread of Quercus forests with Tilia, Ulmus, Fraxinus and Acer below the birch zone. This deciduous forest belt achieved its widest distribution between 10000 and 8500 cal. yrs. ВР at the time when Corylus started to expand in the study area. The gradual increase of the tree PAR for the time window 11600-8150/7900 cal. yrs. BP confirms the afforestation process which was enlarged after 9700 cal. yrs. BP. Moreover, the short-term steep decline of the tree PAR at 8230 cal. yrs. BP (level 275 cm, Fig. 25), particularly manifested by Pinusdiploxylon-type and less by Betula, can be considered as a vegetation response to the 8.2 ky climatic event (Alley, Ágústsdóttir, 2005) at higher altitudes. For the first time evidence of this abrupt cooling was identified in a pollen diagram from the Rila Mountain.
Gradually, Abies steadily established in the vegetation cover while the occurrences of Fagus and Picea remained still rare. A foregoing short-term peak of Abies pollen, registered at 9300 cal. yrs. BP (Fig. 24), coincides with a similar one already recorded from the northwestern part of the mountain (Tonkov et al., 2008, 2013).
The forest composition and the altitudinal vegetation zonation started to change after 8150/7900 cal. yrs. BP. The conifers Abies, Pinus sp. and Pinuspeuce enlarged their areas replacing at many places the birch forests and pushing the mixed oak forests and hazel downslope. Stands of Betula continued to be found within the coniferous belt or above the timber-line. This dynamic transformation lasted for c. 2000 years (pollen zones LM-3 and V-5, Figs 24 and 27) and resulted in the formation of a compact coniferous belt dominated by pines and fir. This change is also supported by the presence of Pinus sp. stomata, most probably originating from Pinusmugo at the elevation of Lake Manastirsko 2 and from Pinus sp. around Peat bog Vodniza. The high PAR of Pinusdiploxylon-type, Pinuspeuce and Abies testifies for a substantial increase in the population density of the coniferous woods, while the deciduous trees Betula, Quercus and Corylus began quickly to decline after 7400 cal. yrs. BP. The presence of Carpinusbetulus, Fagus and Piceaabies remained still restricted.
The paleoecological information from the Seven Rila Lakes presents a synchronous pattern of vegetation changes, characterized by the expansion of Pinus and Abies and a decline of Betula. Fossil stomata of Pinus sp. were determined in the sediments of Lake Ribno (Tonkov et al., 2013) as well as fossil fruits of Betula in the sediments of Lake Sedmo Rilsko. In conformity with the above studies in the Northwestern Rila Mountain, the onset of the important change in the composition of the vegetation cover, confined to c. 8200-8000 cal. yrs. BP, was obviously triggered by a climate shift as shown by the summer and winter reconstructions of temperature and precipitation values across Europe. In summer, relatively cooler and somewhat wetter conditions established in many parts of Southern Europe, while in winter time cooler drier conditions prevailed (Davis et al., 2003; Mauri et al., 2013). The 8.2 ky climatic event probably also influenced this change as the various aspects of this shift may have spread over a period of up to 600 years (Rohling, Palike, 2005). The short-term steep decline of the PAR of trees at 8230 cal. yrs. BP was most clearly established from Lake Manastirsko 2 unlike the situation at Peat bog Vodniza. Quite probably, the reason was the lower ecological sensitivity and response of the tree vegetation to this climatic oscillation at lower altitudes.
The subsequent stage in the vegetation development between 5600/5350 and 3450 cal. yrs. BP manifested the widest distribution of Pinussylvestris, Pinusmugo, Pinuspeuce and Abies in the Central Rila Mountain. The enlargement of the areas occupied by the conifers was facilitated by favorable climatic conditions, and after soils with stable humic horizons had developed (Bennett, Willis, 1995). The regular presence of fossil Pinus stomata confirms that pines were growing around the Peat bog Vodniza, and the high PAR for the coniferous taxa indicates the existence of a dense forest cover (pollen zone V-6, Figs 27 and 28). This vegetation reconstruction is supported also by the PAR of the conifers from the higher located site Lake Manastirsko 2, reaching maximal values at 3400 cal. yrs. BP, and thus, manifesting that the timber-line was placed higher than in present times (pollen zone LM-6, Fig. 25). A characteristic feature was also the slow-rate penetration of Piceaabies into the coniferous belt and the gradual increase of Fagus at lower altitudes after c. 4500 cal. yrs. BP.
The paleoecological evidence from Lakes Ostrezki which extends back to c. 6700 cal. yrs. BP provides valuable information about the distribution of the main tree taxa and the position of the tree-line. The pollen frequencies and the plant macrofossils (needles and seeds) for the time window 6700-3770 cal. yrs. BP point to the existence of stands of Pinusmugo, Juniperussibirica and Alnusviridis at that altitude, among patches of herb vegetation. The high presence of Abies pollen (25-35%) confirms its participation in the composition of the coniferous belt (pollen zone LOS-3, Fig. 32). The tree-line shaped by Pinussylvestris, Pinuspeuce and some Abies was running in close proximity to the lakes, proved by the find of fossil needles and seeds (zone MOS-2, Fig. 34).
After 3400 cal. yrs. BP Piceaabies spread into the coniferous belt and its maximal distribution was attained in the conditions of a changing climate with lower average temperatures and increase in precipitation (van Geel et al., 1998). Pines and fir partly declined while birch slightly increased. Beech also started to enlarge at lower altitudes along the mountain river valleys. The appearance of fossil stomata of Piceaabies and the steep increase of its PAR undoubtedly points that spruce reached the elevation of the Peat bog Vodniza c. 3300 cal. yrs. BP (pollen zone V-7, Figs 27 and 28). A similar age for the expansion of spruce in the study area is obtained from Lake Manastirsko 2 as the pollen curve of Picea starts to rise and the total tree PAR substantially increases since 3400 cal. yrs. BP, attributed mainly to Pinusdiploxylon-type, Pinuspeuce, Abies, Picea (Fig. 25). Thus, the higher located site has also archived the changes in the composition of the coniferous belt and the increasing density of the forest cover at lower elevations.
In the pollen diagrams from Lakes Ostrezki the decline of Abiesc. 3500 cal. yrs. BP is accompanied by a rise of Picea and the apperance of the first macrofossils of spruce (needles) at 2800-2700 cal. yrs. BP (Fig. 34). In comparison, the palynological records from the area of the Seven Rila Lakes indicate also that the first of several expansion maxima of spruce in the Northwestern Rila Mountain was reached c. 2800-2600 cal. yrs. BP.
Indications of human presence are clearly visible in the pollen diagrams of Lake Manastirsko 2 and Peat bog Vodniza after c. 3400 cal. yrs. BP when pollen grains of Hordeum-type and Secale are determined, pointing to agricultural activities in the foothills of the mountain. The increase of both pollen and influx values for Cichoriaceae and Poaceae, the appearance of Plantagolanceolata, Scleranthus, and the rise for Rumex suggest an enlargement of the open area used for seasonal pastures.
In the pollen and plant macrofossil diagrams from Lakes Ostrezki the continuous pollen curves of Plantagolanceolata, Rumex, Scleranthus, Urtica, considered as indicators of human disturbance in mountainous areas, appear at 3770 cal. yrs. BP (pollen zone LOS-3, Fig. 32). Part of Poaceae, Artemisia and Cichoriaceae pollen could be also included in this group. The abundance of charcoal fragments just before 3770 cal. yrs. BP and c. 2800 cal. yrs. BP presumes that some of the forest fires were caused by the local people to extend the areas for high-mountain pasture land. The decline of macrofossils from Pinussylvestris and Pinuspeuce, alongside with the finds from heliophilous herbs like Potentilla sp., Dianthus sp., Silene sp., Doronicumaustriacum, indicates openings in the vegetation cover and lowering of the tree-line.
The first signs of human impact, derived from the area of the Seven Rila Lakes, are comparable with the presence of the anthropogenic indicators Plantagolanceolata and Rumex in the fossil records of Lakes Ostrezki after 3400-3200 cal. yr BP, coinciding with the starting point of increase for Fagus and Piceaabies.
In the vicinity of Lake Suho Ezero-RM forests of Pinussylvestris, Pinuspeuce and stands of Pinusmugo were distributed c. 2500-2000 years ago. The presence of Picea pollen with 10-18% shows that spruce already gained a considerable participation in the composition of the coniferous forests, while Fagus enlarged mainly below 1300 m along the valley of the Rilska river. The rise of Abies pollen curve can be explained with a thinner forest filter and easier pollen transport upslope rather than by an increase of fir in the coniferous woods. The herb vegetation on open places was very diverse in species composition and the presence of anthropophytes as Rumex, Scleranthus and some Chenopodiaceae species is connected with reclamation of new areas for high-mountain pastures (Fig. 39). The general increase of the anthropophytes, accompanied by higher percentage values for Cerealia-type, and the appearance of Triticum-type pollen c. 1400 cal. yrs. BP unequivocally testify to an intensive agricultural activity.
The vegetation development in historical time was characterized by an intensification of the anthropogenic impact, proved by the increase of Cichoriaceae, Plantagolanceolata and Scleranthus pollen, indicative of livestock-grazing in the mountain meadows. After c. 1000 cal. yrs. BP at many places the tree-line was artificially lowered in order to extend pasture land.
The last enlargement of Piceaabies, and partly of Fagus, as recorded from Lake Manastirsko 2 (pollen zone LM-5, Fig. 24) and Peat bog Vodniza (pollen zone V-7, Fig. 27) was reached c. 1700 cal. yrs. BP, and afterwards both trees started to decline. The vegetation development around the Peat bog Vodniza, particularly after 900 cal. yrs. BP, featured an increase of the anthropogenic impact, proved by the rise of pollen for Cichoriaceae, Plantagolanceolata, Plantagomajor/media, Rumex and Scleranthus. Larger areas were occupied by Pinus, mostly Pinusmugo in the subalpine belt. A tendency for a decline of the PAR for Abies, Pinuspeuce, Betula, Quercus, and partly for Picea, is observed after 1500 cal. yrs. BP in the diagrams of Lake Manastirsko 2 (Fig. 25) and Peat bog Vodniza (Fig. 28).
The rather poor macrofossil record in the sediments of Lakes Ostrezki after 1240 cal. yr BP, comprising only scarce needles of Pinusmugo, Juniperussibirica and other occasional finds, reflects the characteristics of the present-day vegetation in the subalpine belt as highly influenced by humans.
This peat bog, a former lake, is situated 6 km westwards from the mountain resort Trestenik at 1900 m (42°03’52.46”N, 23°34’03.32”E) in a glacial valley in the lower of the two troughs. The upper one still contains a lake at 2045 m with open water while the investigated site is filled in with sediments, except for a small streamlet meandering through it (Fig. 3). The peat bog is located close to the timber-line in the coniferous belt. The main tree species are Pinussylvestris, Piceaabies and Pinuspeuce. More rarely are found Abiesalba, Betulapendula and Populustremula. At some places are growing stands of Pinusmugo and Juniperussibirica. The bog vegetation is represented by spots of Sphagnum sp., Vacciniummyrtillus, Bruckenthaliaspiculifolia, Eriophorumvaginatum, Eriophorumlatifolium, Carexcanescens, Carexnigra, Carexechinata, Heleocharispalustris. Near the streamlet are growing Calthalaeta, Geumcoccineum, Cardamineamara, Cardaminerivularis, Saxifragarotundifolia, Ranunculusmontanus, Rumexalpinus, Nardusstricta, Deschampsiacespitosa, etc. (Bozilova, Smit, 1979; Bozilova et al., 1990) (Fig. 40).
114B26DF-C1D0-5972-A0AE-FA1F0AC9B32A
A view of Lake Suho Ezero (Photo: R. Bradshaw).
https://binary.pensoft.net/fig/1672894
<italic>Coring, lithology and radiocarbon dating</italic>
The coring of the lake was performed in the central part with motor Streif sampler in plastic tubes each 100 cm long and 5 cm in diameter. Two cores were obtained in the 1970s. The first core is 920 cm long and the second is 1200 cm long. The lithology of the sediments is: Core-1, 0-680 cm peat, 680-710 cm peaty gyttja, 710-900 cm gyttja and 900-920 cm peaty gyttja; Core-2, 10-630 cm peat, 630-780 cm peaty gyttja, 780-900 cm gyttja, 900-1100 cm grey clay and 1100-1200 cm grey silt. The radiocarbon age of 6 bulk sediment samples (4 from Core-1 and 2 from Core-2) was determined and the results are shown in Table 10. Attempts to obtain radiocarbon dates from the lowermost 200 cm of Core-2 were not successful. The radiocarbon date GrN 10060±130 (11660 cal. yrs. BP) from Core-1 refers to the transition Lateglacial/Holocene but the pollen stratigraphy indicated Lateglacial age (B ozilova, Smit, 1979). This was confirmed after the lower part (500-880 cm) of the Core-1 was re-analyzed in 2012. Therefore, the above radiocarbon date should not be taken into consideration. Quite probably, the sample submitted for dating was contaminated or the sediment was reworked.
Radiocarbon dates from Lake Suho Ezero.
Lab. code
Depth (cm)
14C age (BP)
14C age cal. BP, ±2σ (mid-point)
Material dated
Core-1
GrN
50-55
1620±60
1700-1350 (1525)
peat
GrN
170-180
2185±35
2320-2110 (2205)
peat
GrN
280-300
2880±30
3150-2880 (3015)
peat
GrN
910-920
10060±130
12060-11240 (11650)
peaty gyttja
Core-2
Hv
540-560
5680±75
6640-6310 (6475)
peat
Hv
850-853
10575±220
12960-11750 (12355)
gyttja
<italic>Pollen analysis</italic>
Pollen analysis was performed at 2, 4 or 10 cm interval and two percentage pollen diagrams are constructed (Core-1, Fig. 41; Core-2, Fig. 42). The interval 900-1200 cm of Core-2 appeared rather poor in pollen content. On both pollen diagrams seven local pollen assemblage zones (LPAZs) are recognized (SE-1 to SE-7). Brief descriptions are presented and the percentage values in brackets refer to the relevant pollen taxa in Core-1:
This pollen zone is recognized only in Core-2. Pollen of Pinusdiploxylon-type is 20-35% and of Pinuspeuce 5-8%. Single pollen grains or small quantities are determined from Betula, Ephedradistachya-type, Quercus. The herb pollen taxa dominate, represented by Artemisia 35-40%, Chenopodiaceae 30%, Poaceae 5-10%, Achillea-type, Cichoriaceae, Centaurea, Rumex, Ranunculaceae and Caryophyllaceae.
The total quantity of tree pollen reaches 45-50% (20%), contributed by Pinusdiploxylon-type 30-35% (20%), Betula 13% (5%), Pinuspeuce 3-5%, Quercus 2%, Alnus, Salix, etc. The presence of herb pollen taxa declines but their variety increases as shown by Artemisia 12% (30-20%), Chenopodiaceae 5-10% (17-10%), Poaceae up to 20%, Achillea-type 5-7%, Apiaceae 7%, Rumex, Caryophyllaceae, Galium-type, Plantagomajor/media-type, etc.
The total tree pollen curve sharply decreases to 20% (10%) and low frequencies are registered for Pinusdiploxylon-type 10% (5%), Pinuspeuce 1-2%, Betula 3%, Quercus 2%, Corylus (2%). Pollen of both Ephedra types (distachya and fragilis) is also established. The rest of the tree taxa are absent or represented by single pollen grains. The main herb pollen taxa such as Artemisia 25-35% (up to 40%), Chenopodiaceae 12% (up to 30%), Poaceae 15-20% increase again.
The total tree pollen curve rises quickly to 65-70% (80%), attributed to Betula 15-20% (30%), Quercus 15% (30-40%), Ulmus and Tilia each with 3-5%, Corylus 10%, Juniperus 2% (8%). The pollen curves of Carpinusbetulus, Carpinusorientalis/Ostrya and Acer appear. Minor values for Abies and Fagus are recorded in Core-1. The lowest values for Pinusdiploxylon-type 5-8% are registered after a short-term maximum of 18% in Core-1 (level 700 cm). Pollen grains of Juglans, Humulus/Cannabis-type and Vitis are also determined. The herb pollen taxa are represented by Poaceae 15-18% (up to 12%), Ranunculaceae 5%, Rumex 8% (5%), Apiaceae 5% (up to 10%), Artemisia up to 5%, Chenopodiaceae 3%, Rosaceae, Dianthus-type, etc. The continuous presence of spores of Polypodiaceae begins in this zone.
The presence of Pinusdiploxylon-type increases to 50% (45-60%), Pinuspeuce up to 12% (20%) and Abies 5-8% (up to 10-15%). The pollen frequencies of Betula, Quercus, Corylus and Alnus decline to 8% (10%), 5-7% (10%), 3% (7%) and 2%, respectively. Low quantities of Fagus and Picea pollen are recorded in almost all samples. The total herb pollen decreases to 18% (10%) and new pollen taxa are Triticum-type, Secale, Plantagolanceolata, Viola, Filipendula. Pollen grains of Typha/Sparganium-type, Potamogeton and spores of Sphagnum are also present.
The pollen values of Pinusdiploxylon-type reach 60-65% and those of Abies 15-20%. In this zone appears the pollen curve of Fagus up to 5% (8%). The presence of Picea increases steeply to 15-18% (25%). The herb pollen taxa are represented by Poaceae, Artemisia, Cichoriaceae and the participation of Plantagolanceolata, Ranunculus-type, Sanguisorbaminor, Rumex, Scleranthus pollen is regular.
The pollen curve of Pinusdiploxylon-type fluctuates around 40-50% (40-60%), accompanied by Picea 10% (up to 15%), Pinuspeuce 5-12% (up to 20%), Abies 10% (5%), Fagus 7-8% (15-5%), Quercus 10%, Corylus 5%, Juniperus, Salix and Carpinus. Pollen grains of Juglans are regularly found. Pollen of Poaceae reaches maximal values of 15-30% (20%) and the presence of Achillea-type, Rumex, Ranunculaceae, Plantagomajor/media-type, Plantagolanceolata, Cerealia-type, Secale and Triticum-type pollen is worth to be mentioned. The increase of Cyperaceae pollen and the decline of Polypodiaceae spores are recorded.
<italic>Plant macrofossil analysis</italic>
The Core-2 was sampled also at 15-25 cm interval. Plant macrofossils were not established in the intervals 915-1120 сm and 0-50 cm. The frequency of the macrofossils found is shown in absolute numbers (Fig. 43) and five local macrofossil assemblage zones (LMAZs) are distinguished (MSE-1 to MSE-5). Brief descriptions are as follows:
6CFE0764-B7FB-5E4A-A8BC-77F9898131EA
Plant macrofossil diagram of Lake Suho Ezero-2.
https://binary.pensoft.net/fig/1672899
LMAZ MSE-1 (915-825 сm)
Several seeds of Silene sp., Juncus sp., Bruckenthaliaspiculifolia, fruits of Carex sp. and a needle of Pinuspeuce are determined.
LMAZ MSE-2 (825-600 сm)
A characteristic feature is the abundance of fruits and bud-scales of Betula. Needles and bud-scales of Pinus sp. (Pinussylvestris, Pinusmugo and Pinuspeuce), seeds of Juncus sp., Cardamine sp., Bruckenthaliaspiculifolia, Silene sp. and fruits of Carex sp. are present.
LMAZ MSE-3 (600-310 сm)
Needles of Pinuspeuce and Pinus sp., bud-scales от Pinus sp. are determined. The number of Betula fruits is lower compared to the previous zone. Seeds of Juncus sp., Bruckenthaliaspiculifolia, Silene sp. and fruits of Carex sp. are found.
LMAZ MSE-4 (310-170 сm)
Needles and seeds of Piceaabies appear in this zone. The number of needles and bud-scales of Pinus sp. increases. There are well preserved male cones of Pinusmugo, needles of Pinuspeuce, fruits of Betula and Carex sp., seeds of Juncus sp., Apiaceae and Potentilla sp.
LMAZ MSE-5 (170-50 сm)
The number of plant macrofossils is rather low, including sporadical finds of Pinus sp. and Pinuspeuce needles, seeds of Potentilla sp. and fruits of Carex sp.
Peat bog Vapsko 1 (site 13)
This peat bog is situated in a depression in the lower part of the subalpine belt at 2143 m (42°04’34.04”N, 23°31’25.84”E) just above the present tree-line (Fig. 3). The peat bog has a nearly rectangular shape and is about 50 m long and 10-15 m wide. It is surrounded by groups of Pinusmugo and Juniperussibirica within patches of herb vegetation. Single trees of Pinuspeuce, Pinussylvestris and Piceaabies are found to the east and west of the coring place. Stands of Betulapendula and Sorbusaucuparia grow close to the tree-line. The bog surface is overgrown by hummocks of Sphagnum sp., Carexnigra, Carexrostrata, Nardusstricta, Agrostiscapillaris, Eriophorumlatifolium, Veratrumlobelianum, etc. (Fig. 44). The coniferous forest belt in this part of the mountain is dominated by Pinuspeuce, admixed with Piceaabies and Pinussylvestris. The recent distribution of Fagussylvatica is fragmented and restricted at altitudes below 1200-1000 m together with the oak forests (Tonkov et al., 2018).
307A4208-09E9-520F-A596-A0874635B2B1
A view of Peat bog Vapsko 1 (Photo: S. Tonkov).
https://binary.pensoft.net/fig/1672900
<italic>Coring, lithology and radiocarbon dating</italic>
The sediment core is 150 cm long and was collected with Dachnowsky hand-coring equipment from the central part of the peat bog. The lithology of the sediments is: 0-40 cm slightly decomposed Sphagnum-Cyperaceae peat, 40-135 cm Cyperaceae peat and 135-150 cm clay with fine sand. The radiocarbon age of 4 bulk sediment samples was determined and the results are shown in Table 11. The age of the core is c. 10000 cal. yrs. BP.
Radiocarbon dates from Peat bog Vapsko 1.
Lab. code
Depth (cm)
14C age (BP)
14C age cal. BP, ±2σ (mid-point)
Material dated
RICH-23864
23-26
2171±28
2310-2060 (2185)
peat
UBA-21556
47-50
4046±33
4790-4420 (4605)
peat
UBA-21557
97-100
6143±40
7170-6930 (7050)
peat
UBA-21558
147-150
8867±52
10180-9740 (9960)
clay with sand
<italic>Pollen analysis</italic>
Pollen analysis was performed at 5 cm interval and a percentage pollen diagram is constructed (Fig. 45). Pollen accumulation rates (PAR) for the major tree/shrub and herb taxa are also calculated (Fig. 46). Four local pollen assemblage zones (LPAZs) can be delimited (VP-2 to VP-5). Brief descriptions are as follows:
Pollen accumulation rates (PAR; pollen grains cm-2 yr-1) for the main tree/shrub and herb taxa from Peat bog Vapsko 1 plotted against age in cal. yrs. BP.
https://binary.pensoft.net/fig/1672903
LPAZ VP-2 (150-113 cm, Betula-Quercetum mixtum-Corylus-Pinus) (10000-7900 cal. yrs. BP)
The tree pollen dominates with 50-65%, attributed to Betula 17%, Pinusdiploxylon-type 10% with a short-term peak of 30% (level 135 cm), Pinuspeuce and Juniperus each below 5%, Corylus 10-15%, Quercusrobur-type 10%, Quercuscerris-type 7% and Tilia 6%. Low pollen frequencies of Abies, Carpinusbetulus, Carpinusorientalis/Ostrya, and traces of Fagus, Picea, Vitis and Hedera pollen are found. The herb pollen taxa are represented by Poaceae and Apiaceae each up to 13-15%, Cirsium-type 10-5%, Artemisia 5%, Rumex 5%, Ranunculus-type, Brassicaceae, Dianthus-type, etc. High values of Polypodiaceae spores 10-17% are recorded. The total PAR of tree taxa is from 1000 to 3000 grains cm-2 yr-1, contributed by Pinusdiploxylon-type up to 1000, Betula 400 up to 750, Quercusrobur-type up to 370, Corylus 350-450. The total PAR of herb taxa is up to 1750, represented by Poaceae 350-400, Apiaceae 250 (maximum 600), Rumex 150.
LPAZ VP-3 (113-77 cm, Pinus-Abies-Betula-Corylus) (7900-5900 cal. yrs. BP).
The pollen curve of Pinusdiploxylon-type rises to 40-70%, Pinuspeuce 5-10%, Corylus 10-15%, Betula 13%, Quercusrobur-type and Quercuscerris-type each with 5%. Subsequently, pollen of deciduous trees from Betula, Quercusrobur-type, Quercuscerris-type, Corylus, Tilia and Ulmus quickly declines. The continuous pollen curve of Abiesappears with 2-5% and then increases to 12%. Sporadical pollen grains of Picea, Carpinusbetulus and Acer are found. The total herb pollen is 5-10%, and the main taxa are Poaceae, Cirsium-type, Brassicaceae, Apiaceae and Rumex. The total PAR of tree taxa is from 1200 to 3500 grains cm-2 yr-1, contributed by Pinusdiploxylon-type 50-2500, Pinuspeuce up to 300, Betula 250-300, Corylus 200-350, Abies 100 (up to 350). The total PAR of herb taxa declines to 250-700, represented by Poaceae 200, Apiaceae 150-200.
LPAZ VP-4 (77-37 cm, Pinus-Abies) (5900-3500 cal. yrs. BP)
The coniferous pollen dominates represented by Pinusdiploxylon-type 80%, Pinuspeuce 8-10% and maximal values for Abies 12-15%. Pollen of deciduous trees such as Betula, Alnus, Quercus, Carpinusbetulus, Carpinusorientalis/Ostrya, Tilia, Corylus is constantly present with rather low frequencies. Pollen of Fagus and Picea is recorded in all samples with 1-2%. The most common herb pollen taxa are Poaceae up to 8%, Artemisia, Apiaceae, Cirsium-type, Chenopodiaceae, Ranunculus-type, Dianthus-type, Brassicaceae, etc. The total PAR of tree taxa reaches maximal values of 4000-6000 grains cm-2 yr-1, due to Pinusdiploxylon-type 2500-4500, Abies 600-800, Pinuspeuce up to 350, Corylus 50-100. The total PAR of herb taxa is up to 500.
LPAZ VP-5 (37-0 cm, Pinus-Picea-Fagus-Abies) (3500 cal. yrs. BP-until present)
The pollen curves of Picea 8% and Fagus 5% rise, while pollen of Pinusdiploxylon-type and Abies declines to 50% and 3-5%, respectively. The presence of Pinuspeuce remains unchanged. Minor values below 2-3% are recorded for Betula, Alnus, Corylus, Quercusrobur-type, Quercuscerris-type, Carpinusbetulus and Juniperus. Pollen of Humulus/Cannabis-type, Vitis and Vaccinium-type is occasionaly found. The presence of herb pollen taxa increases to 30%, attributed mainly to Poaceae 15%, Artemisia and Apiaceae each with 2-3%, Chenopodiaceae, Achillea-type, Brassicaceae, Campanulaceae, etc. The continuous presence of Plantagolanceolata and Scleranthus pollen is recorded in this zone. Pollen of Secale is also determined. The total PAR of tree taxa declines from 2000 to 800 grains cm-2 yr-1, due to Pinusdiploxylon-type 1500-500, Abies 100, Pinuspeuce 150-50, unlike the presence of Picea up to 220 and Fagus up to 150.
Peat bog Vapsko 2 (site 14)
This peat bog is located at 2120 m (42°04’26.85”N, 23°31’27.81”E) in the lower range of the subalpine belt, at the present timber-line, c. 220 m southeast from the Peat bog Vapsko 1 (Fig. 3). The peat bog is about 90 m long and 20-35 m wide, surrounded by dense stands of Pinusmugo with some Juniperussibirica, Piceaabies and Pinuspeuce to the north, northwest and southwest. To the east the peat bog borders a steep high slope overgrown by Pinusmugo and scattered trees of Pinuspeuce. The bog surface is covered by hummocks of Sphagnum sp., Carexnigra, Carexrostrata, Deschampsiacespitosa, Nardusstricta, Eriophorumlatifolium, Potentillapalustris, Veratrumlobelianum, Rumexalpinus, Calthalaeta, Plantagogentianoides, Gentiananivalis, etc. (Tonkov et al., 2019) (Fig. 47)
5EFFC9DD-3C68-5539-B23C-6B403C32F3BB
A view of Peat bog Vapsko 2 (Photo: S. Tonkov).
https://binary.pensoft.net/fig/1672904
<italic>Coring, lithology and radiocarbon dating</italic>
The sediment core is 305 cm long and was collected with Dachnowsky hand-coring equipment from the deepest part of the peat bog. The lithology of the sediments is: 0-195 cm slightly decomposed sedge peat with plant remains, 195-280 cm peaty gyttja and 280-305 cm gyttja with fine sand. The radiocarbon age of 10 samples (3 of plant macrofossils and 7 of bulk sediment) was determined and the results are shown in Table 12. The age of the core is 12100 cal. yrs. BP.
Radiocarbon dates from Peat bog Vapsko 2.
Lab. code
Depth (cm)
14C age (BP)
14C age cal. BP, ±2σ (mid-point)
Material dated
DeA-10895
24
2121±26
2290-2000 (2095)
peat
DeA-10105
55
3636±30
4080-3860 (3970)
wood
DeA-10896
72
4333±29
4970-4840 (4905)
peat
RICH-21695
102-104
4778±37
5600-5330 (5465)
peat
DeA-10106
142
5165±32
6000-5760 (5880)
seed
RICH-21694
194-196
6417±44
7430-7260 (7345)
peat
DeA-10897
215
7605±48
8540-8340 (8440)
peaty gyttja
DeA-10107
237
8700±58
9890-9540 (9715)
wood
DeA-10898
273
9153±46
10490-10220 (10355)
peaty gyttja
RICH-21693
302-304
10301±51
12390-11830 (12110)
gyttja with fine sand
<italic>Pollen analysis</italic>
Pollen analysis was performed at 5 cm interval and a percentage pollen diagram is constructed (Fig. 48). Pollen accumulation rates (PAR) for the major tree/shrub and herb taxa are also calculated (Fig. 49). Fossil stomata in low number from Pinus sp., Juniperus sp. and Abies were occasionally found on the pollen slides from 13 sample depths and their presence (*) is also shown on the pollen diagram. Five local pollen assemblage zones (LPAZs) can be delimited on the pollen diagram (VP-1 to VP-5) (Figs 48 and 7). The palynostratigraphical correlation of the cores from peat bogs Vapsko 1 and Vapsko 2 is feasible due to the similarities in the behaviour of the main pollen curves and the application of the depth/age model constructed for the Peat bog Vapsko 2. Brief descriptions of the pollen zones are as follows:
Pollen accumulation rates (PAR; pollen grains cm-2 yr-1) for the main tree/shrub and herb taxa from Peat bog Vapsko 2 plotted against age in cal. yrs. BP.
https://binary.pensoft.net/fig/1672907
LPAZ VP-1 (305-292 cm, Artemisia-Chenopodiaceae-Poaceae) (12100-11600 cal. yrs. BP)
The herb pollen taxa dominate, attributed to Artemisia 35-40%, Chenopodiaceae 10-12%, Poaceae 16%, Rumex 6%, Apiaceae 5%, etc. The tree pollen constitutes only 20%, represented by Pinusdiploxylon-type 10%, Betula and Pinuspeuce each below 5%, minor values for Juniperus, Quercus, Corylus. The total PAR is rather low 1000-2000 grains cm-2 yr-1 with the prevailance of the herbs such as Artemisia 500-750, Poaceae 250-350 and Chenopodiaceae 200.
LPAZ VP-2 (292-207 cm, Betula-Quercetum mixtum-Corylus-Pinus) (11600-7980 cal. yrs. BP)
The quantity of tree pollen quickly rises to 35-75%, due to Betula up to 27%, Quercuscerris-type 10-18%, Quercusrobur-type 10%, Corylus with a maximum of 18%, Ulmus, Tilia, Hedera, Vitis, etc. The coniferous pollen is represented by Pinusdiploxylon-type 10%, Juniperus 5%, Pinuspeuce 5%. Fossil stomata of Pinus sp. and Juniperus sp. are determined. The herb pollen values decline, contributed mainly by Poaceae 10-25%, Artemisia, Rumex, Cirsium-type, Apiaceae each with 5%. The maximal presence of Polypodiaceae spores with 15% is recorded. The total PAR of tree taxa increases and reaches 5000 grains cm-2 yr-1, attributed to Betula up to 2000, Quercus up to 1600, Ulmus and Tilia each with 400, Pinusdiploxylon-type up to 400-600. The total PAR of herb taxa attains maximal values of c. 2000-2500, contributed mainly by Poaceae 1000, Artemisia, Chenopodiaceae and Cirsium-type each with 100-300.
LPAZ VP-3 (207–142 cm, Pinus-Abies-Betula-Corylus) (7980-5900 cal. yrs. BP)
The pollen curve of Pinusdiploxylon-type rises to 65% and Pinuspeuce displays a maximal value of 18%. The continuous pollen curve of Abiesappears and reaches 10%. The deciduous tree pollen is represented by Betula and Corylus each up to 10%, Quercuscerris-type 8%, Quercusrobur-type, Tilia, Ulmus and Carpinus each less than 5%. Fossil stomata of Juniperus and Abies are determined. The diversity of herb pollen taxa is high but they are present with minor values, except for Poaceae with 8%. Pollen of Cyperaceae shows a maximum of 10%. Compared to the previous zone, the total PAR of tree taxa retains its value of c. 5000 grains cm-2 yr-1 but contributed now by Pinusdiploxylon-type c. 2500, Pinuspeuce up to 1000, Abies 500, Corylus up to 400.
LPAZ VP-4 (142-47 cm, Pinus-Abies) (5900-3500 cal. yrs. BP)
In this zone pollen of Pinusdiploxylon-type dominates with 75%, Pinuspeuce 15% and Abies 10-15%. Fossil stomata of Pinus sp., Juniperus sp. and Abies are determined. In the upper part of the zone the continuous pollen curves of Fagus and Picea appear each below 5%. There are no changes in the participation of the herb pollen taxa. The total PAR of tree taxa attains maximal values of c. 12500-18000 grains cm-2 yr-1, due to Pinusdiploxylon-type up to 10000, Pinuspeuce 2000-2500 and Abies 2000.
LPAZ VP-5 (47-0 cm, Pinus-Picea-Fagus-Abies) (3500 cal. yrs. BP-until present)
The pollen curves of Pinusdiploxylon-type and Pinuspeuce decline to 40-60% and 5%, respectively, while Fagus and Picea are represented with 5%. Minor values are recorded for deciduous tree pollen of Quercuscerris-type, Quercusrobur-type, Betula, Corylus, Carpinus, etc. The quantity of herb pollen increases, attributed to Poaceae 15%, Cichoriaceae 20%, Brassicaceae, Apiaceae, Artemisia, Plantagolanceolata, Secale, etc. The total PAR of tree taxa declines to 2500-5000 grains cm-2 yr-1 but the maximal values for Picea and Fagus up to 400-600 and 200-300, respectively, shoud be mentioned. The total PAR of herb taxa marks an increase to 1000-1500.
Lake Vapsko 2 (site 15)
This lake is situated in the lower range of the subalpine belt at 2250 m (42°04’50.72”N, 23°31’11.50”E) in this part of the Rila Mountain (Fig. 3). It has a nearly oval shape with a water surface of 0.28 ha fed by the larger upper Lake Vapsko 1 (2268 m) and drains into the Vapa river. The surrounding steep slopes are covered by thick impenetrable stands of Pinusmugo with some Juniperussibirica within patches of herb vegetation (Ivanov, 1964). The flat peaty shores of the lake are overgrown by hummocks of Sphagnum sp., Carexnigra, Carexrostrata, Trichophorumcespitosum, Deschampsiacespitosa, Nardusstricta, Eriophorumlatifolium, Parnassiapalustris, Veratrumlobelianum, Primuladeorum, Plantagogentianoides, Pinguiculabalcanica, Pseudorchisalbida, etc. (Tonkov et al., 2023) (Fig. 50).
30BD2AB6-40CD-59A0-B13F-A3B31C256950
A view of Lake Vapsko 2 (Photo: S. Tonkov).
https://binary.pensoft.net/fig/1672908
<italic>Coring, lithology and radiocarbon dating</italic>
The sediment core is 500 cm long and was collected with Dachnowsky hand-coring equipment from the southeast peaty shore at a water depth of 20 cm (Fig. 50a). The lithology of the sediments is: 0-120 cm peat with plant remains, 120-267 cm peaty gyttja with fine sand, 267-274 cm sand, 274-327 cm peaty gyttja with fine sand, 327-335 cm sand and 335-500 cm peaty gyttja with fine sand. The radiocarbon age of 5 bulk sediment samples was determined and the results are shown in Table 13. The age of the core is estimated at c. 6200 cal. yrs. BP (To nkov et al., 2023).
Radiocarbon dates from Lake Vapsko 2.
Lab. code
Depth (cm)
14C age (BP)
14C age cal. BP, ±2σ (mid-point)
Material dated
Ua-59524
100-102
1307±30
1300-1170 (1235)
peat with plant remains
Ua-59525
200-202
3157±33
3460-3260 (3360)
peaty gyttja with fine sand
Ua-59526
300-302
4292±32
4960-4820 (4890)
peaty gyttja with fine sand
Ua-60670
385-387
5032 ±37
5900-5660 (5780)
peaty gyttja with fine sand
Ua-59528
492-494
5439±35
6310-6120 (6215)
peaty gyttja with fine sand
<italic>Pollen analysis</italic>
Pollen analysis was conducted at 10 cm interval and a percentage pollen diagram is constructed (Fig. 51). Pollen accumulation rates (PAR) for the major tree/shrub and herb taxa are also calculated (Fig. 52). On the pollen diagram four local pollen assemblage zones (LPAZs) can be recognized (LV-1 to LV-4). Brief descriptions are as follows:
20526E0E-F756-547B-BBAD-F614D4FF6BC2
Coring at Lake Vapsko 2. From left to right: Dr. G. Wolff and the author (Photo: E. Marinova).
Pollen accumulation rates (PAR; pollen grains cm-2 yr-1) for the main tree/shrub and herb taxa from Lake Vapsko 2 plotted against age in cal. yrs. BP.
https://binary.pensoft.net/fig/1672911
LPAZ LV-1 (490-425 cm, Pinus-Abies) (~6200-5940 cal. yrs. BP)
The total tree pollen dominates with 85-90%, due to Pinusdiploxylon-type 55-60%, Abies 10-12%, Pinuspeuce up to 10%, Corylus 5%, Quercus, Betula and Carpinus each below 5%. The herb pollen is represented by Poaceae, Rumex, Apiaceae each below 5%. Spores of Polypodiaceae are also present. The total PAR of tree taxa ranges from 80000 to 50000 grains cm-2 yr-1, contributed mainly by Pinusdiploxylon-type up to 50000, Pinuspeuce up to 9000, Corylus up to 3000, Betula and Quercuscerris-type each up to 1500, etc.
LPAZ LV-2 (425-265 cm, Pinus-Abies-Fagus-Picea) (5940-4340 cal. yrs. BP)
In this zone the regular presence of Fagus and Picea pollen begins although with low frequencies. There are no changes in the participation of the other tree taxa. The first occurrence of Juglans pollen is recorded. For the herb pollen taxa shoud be mentioned the find of Plantagolanceolata and spores of Selaginellaselaginoides. The total PAR of tree taxa declines from 80000 to a stable value of c. 20000 grains cm-2 yr-1, attributed to Pinusdiploxylon-type 50000-18000, Pinuspeuce 2500-1000, Corylus up to 500, Abies from 1000 to 250. The values for Fagus and Picea average c. 250. The total PAR of herb taxa fluctuates c. 5000.
LPAZ LV-3 (265-135 cm, Pinus-Picea-Fagus-Abies) (4340-1950 cal. yrs. BP)
This zone marks the gradual rise of the pollen curves of Fagus and Picea which keep values below 10%. The dominance of Pinusdiploxylon-type pollen continues with c. 60%, accompanied by Pinuspeuce with 5-7%. The pollen curve of Abies declines from 14% to 5% at the transition to the next zone. The deciduous tree pollen participates with low frequencies of Quercus, Alnus, Corylus, Carpinus, etc. The herb pollen is represented by Poaceae up to 10%, Cichoriaceae, Artemisia, Rumex, Brassicaceae, Apiaceae, etc. Pollen of Plantagolanceolata is regularly found. The total PAR of tree taxa is c. 20000 grains cm-2 yr-1, attributed to Pinusdiploxylon-type c. 10000, Pinuspeuce below 1000, Picea up to 750, Fagus 500, Abies, and the rest of deciduous trees each below 250. The total PAR of herb taxa is c. 2500, represented by Poaceae with less than 1000, Cichoriaceae and Rumex with c. 250 each.
LPAZ LV-4 (135-0 cm, Pinus-Fagus-Picea) (950 cal. yrs. BP-until present)
The total tree pollen reaches 95%, due to Pinusdiploxylon-type up to 85%, Picea 7%, Pinuspeuce 5%, Fagus and Abies each below 2%. Deciduous tree pollen is sporadically determined. No important changes are recorded for the herb pollen taxa but the find of Secale pollen is worth to be mentioned. The pollen curve of Cyperaceae slightly increases. The total PAR of tree taxa is c. 20000 cm-2 yr-1, contributed by Pinusdiploxylon-type 10000-12000, Fagus 1000-1400, Picea up to 1250, Pinuspeuce up to 1000. The total PAR of herb taxa does not exceed 2500, with some increase for Poaceae and Cichoriaceae.
Fossil stomata were found and counted on the pollen slides. Their presence at the relevant depths is indicated on the pollen diagram in absolute numbers (Fig. 51). Two types of stomata were identified originating from Juniperus sp. and Pinus sp. in the interval 490-100 cm (c. 6200-1200 cal. yrs. BP). Most common and larger in number are the stomata from Juniperus sp. in the interval 490-320 cm (c. 6200-5200 cal. yrs. BP) which coincides with the highest influx values of junipers. In the samples above 320 cm their presence and number decreases. The stomata from Pinus sp. are less in number and can not be identified at species level by their observed morphological features. Taking into consideration the location of the lake in the subalpine belt it can be suggested that most of them originated from Pinusmugo. Stomata were not found in the uppermost 100 cm of the core which is explained by unfavorable conditions for their preservation.
3.7 Vegetation history in the Southwestern Rila MountainLateglacial
The palynological and macrofossil results coupled with the radiocarbon dates provide reliable information on the changes in the vegetation and climate in the Southwestern Rila Mountain in postglacial time. The estimated age of Core-2 from Lake Suho Ezero is probably close to the age of the sediment cores collected from the cirque of the Seven Rila Lakes, i.e. older than 16000 cal. yrs. BP. The possibility of earlier sedimentation is also not ruled out, given the lower elevation of 1900 m at which this former lake is located. The pollen stratigraphy and the radiocarbon date 10575±220 14C yrs. BP (12355 cal. yrs. BP) confirm the presence of lateglacial sediments. A close age 10301±51 14C yrs. BP (12110 cal. yrs. BP) was obtained from the bottom part of the core from Peat bog Vapsko 2.
The changes in the vegetation are in many aspects similar and synchronous to those established from other parts of the mountain. The termination of the Pleniglacial and the beginning of the Lateglacial was characterized by a wide distribution of cold- and drought-resistant herb vegetation of "mountain-steppe“ character with dominance of Artemisia, Chenopodiaceae and Poaceae, with the participation of Cichoriaceae, Achillea, Galium, Cirsium and Caryophyllaceae species. Isolated stands of pines (Pinussylvestris, Pinusmugo, Pinuspeuce), Betula and Ephedra shrubland were also found (pollen zone SE-1, Fig. 42). It is assumed that stands of deciduous trees such as Quercus, Carpinusbetulus, Corylus, Ulmus, Tilia were preserved in suitable habitats with sufficient air and soil moisture al lower elevations in the mountain zone 800-1000 m.
The improvement of the climate during the Bölling/Alleröd interstadial complex is reflected in pollen zone SE-2 (Fig. 42) when a number of tree species (Pinussylvestris, Pinuspeuce, Pinusmugo, Betula, Alnus, Salix, Quercus, etc.) migrated along the mountain slopes and enlarged their presence. The herb communities remained dominant in the area around Lake Suho Ezero with an increase in the participation of Poaceae, Achillea, Apiaceae and Rumex species at the expense of Artemisia and Chenopodiaceae. In addition, a change in the lithological composition of the sediments from grey clay to gyttja with a higher content of organic material is established (level 900 cm, Fig. 42).
The last climatic deterioration at the end of the Lateglacial, the Younger Dryas stadial, is documented in the pollen and plant macrofossil records from Lake Suho Ezero (zones SE-3 and MSE-1, Figs 42 and 43) and from Peat bog Vapsko 2 (pollen zone VP-1, Fig. 51). The re-advance of the herb vegetation triggered a retreat of the stands of coniferous and deciduous trees, but, in comparison to the Northwestern Rila Mountain, the role of Poaceae species increased. Of the few macrofossils represented mainly by seeds of herb plants is important to focus on the find for the first time of needles of Pinuspeuce in the Rila Mountain at 12355 cal. yrs. BP. This result confirms the local survival of this tree during the Lateglacial (Tonk ov, 2024).
At higher elevation, in the area of the Vapski peat bogs, the pollen assemblages also revealed typical glacial conditions during the second half of the Younger Dryas stadial. The vegetation was dominated by open herb communities composed of Artemisia, Chenopodiaceae, Poaceae, and other cold-resistant species from Achillea, Cirsium, Cichoriaceae, Rumex, Galium, Apiaceae and Dianthus, confirmed also by their high PAR (pollen zone VP-1, Fig. 49). Single pine trees (Pinusmugo, Pinussylvestris, Pinuspeuce) and Betula, as well as shrubland of Juniperus, were also distributed. The insignificant quantities of pollen from Alnus, Quercus, Corylus and Tilia, evidently air-transported upslope, indicate that these deciduous trees were sheltered at lower altitudes.
Holocene
The transition Lateglacial to Holocene is clearly delimited in the pollen and plant macrofossil diagrams from Lake Suho Ezero and Peat bog Vapsko 2 by the rapid increase of the total tree pollen, the appearance of macroremains from Betula, and, subsequently from Pinus sp., Pinuspeuce and Populustremula. Stands of Betula and Pinus replaced the herb communities dominated by Poaceae, Artemisia and Chenopodiaceae. At lower elevations started the expansion of the mixed oak forests with considerable participation of Ulmus, Tilia, Fraxinusexcelsior, Acer, and later on, Corylus and Carpinusbetulus (zones SE-4 and MSE-2, Figs 42 and 43).
The palynological records from higher altitude confirmed also that, initially, forests of Betula and stands of Pinus and Juniperus, with undergrowth of ferns, had colonized areas on barren soils (pollen zone VP-2, Figs 45 and 48). They reached maximal distribution between 10500 and 9800 cal. yrs. BP. The local presence of Pinus and Juniperus in the near vicinity of the peat bogs was justified by the find of microscopic fragments of leaf fossils with their diagnostic stomata preserved (Fig. 48).
Wood from Salix sp., fruits from Betula sp. and Alnusviridis, seeds from Juniperuscf.sabina, Vacciniumcf.myrtillus, Poaceae, Asteraceae, Apiaceae were determined, particularly after 9500 cal. yrs. BP in the sediments of Peat bog Vapsko 1 (Hoevers, 2017).
The pollen spectra indicate widespread of oak forests with Tilia, Ulmus, Fraxinus below the birch zone, and the expansion of Corylus on more open terrains started after 9800 cal. yrs. BP. The reconstruction of the bog vegetation revealed that it consisted mainly of Poaceae, Artemisia, Achillea, Cirsium, Cichoriaceae, Apiaceae, Rumex and Cyperaceae species.
In the vicinity of Lake Suho Ezero the vegetation was stabilized, dominated by communities of Betula with groups of Pinus and Juniperus which shaped the upper timber-line. Below the birch zone the mixed oak forests climbed higher, compared to the present-day situation, but did not reach the area of the lake as plant macroremains from deciduous trees were not found.
An important change in the composition of the vegetation cover is registered after c. 7900 cal. yrs. BP when the conifers Pinus sp., Pinuspeuce and Abies expanded, replacing at many places the birch forests. Compared to the previous vegetation stage, the total PAR of tree taxa recorded from Peat bog Vapsko 2 retains its values but was contributed mainly by Pinus, Pinuspeuce, Abies and Corylus (pollen zone VP-3, Fig. 49). The deciduous oak forests and Corylus retreated to lower altitudes and their wider distribution ended c. 5900 cal. yrs. BP. The herb vegetation of the peat bogs was enriched with various representatives from Cyperaceae, Artemisia, Cichoriaceae, Rumex, Apiaceae, Galium and Cirsium.
The fossil record from Lake Suho Ezero (zones SE-5 and МSE-3, Figs 42 and 43) reveals also the rapid spread of the conifers as well as the wider presence of Carpinusbetulus, partly on the place of the mixed oak forests. The lake already started to turn into a large peat bog within the coniferous forests. An important feature is the appearance of still isolated groups of Fagus and Piceaabies. The abundance of fossil leaves and bud-scales from Pinuspeuce and Pinus sp. confirms this important change in the composition of the forest vegetation. Also, needles from Pinusmugo/sylvestris, Pinuspeuce and seeds from conifers were established in the sediments of Peat bog Vapsko 1 (Hoevers, 2017).
After 5900 cal. yrs. BP Pinus and Abies retained their dominant role in the forest cover at mid-high altitudes and reached maximal distribution, as clearly supported by the higher values of PAR of the coniferous trees such as Pinusmugo, Pinussylvestris, Pinuspeuce and Abies (pollen zone VP-4, Figs 46 and 49). In the study area Piceaabies and Fagus established permanently c. 5100 cal. yrs. BP and both trees commenced gradually to enlarge areas after c. 4500 cal. yrs. BP. In the deciduous oak forests the participation of Tilia, Ulmus, Carpinus and Corylus was reduced.
The reconstruction of the vegetation c. 6000 cal. yrs. BP at the elevation of the highest investigated site Lake Vapsko 2 presents that stands of Pinus (most likely Pinusmugo) and Juniperus occupied the surrounding slopes. At lower altitudes were distributed Pinuspeuce, Abies, some Betula and groups of Alnus in wetter places and along mountain brooks. The presence of deciduous tree pollen (Quercus, Tilia, Carpinus, Corylus) can be explained by aerial upslope transport from the mixed oak forests. The participation of Fagus remained sporadical while Piceaabies was still absent. The open area around the lake was overgrown by Poaceae, Artemisia, Cichoriaceae, Cirsium, Rumex, Dianthus, Brassicaceae and Apiaceae species (pollen zone LV-1, Fig. 51). Subsequently, the vegetation composition started to change as shown by the appearance of pollen of Picea and Fagus, although with minimal quantities until c. 4300 cal. BP. Then, the presence of both trees increased gradually and they established as permanent forest components in the study area. Pinus and Abies retained their dominant role in the coniferous vegetation.
The paleobotanical evidence from Lake Suho Ezero confirms the dominance of the coniferous forests when the maximal distribution of Abies, Pinussylvestris and, possibly of Pinusmugo communities, was attained. It can be assumed on the basis of the pollen data that the coniferous forest belt climbed c. 200 m higher than nowadays. This assumption is justified by the determination of fossil wood from Abiesalba, Pinuspeuce, Piceaabies, Pinusmugo, Betula and Salix between 3000 and 2220 cal. yrs. BP in Core-1 (Chakalova, Dimitrova, 1980). It is also worth to mention the start of an increase and more noticeable presence of Fagus in the Southwestern Rila Mountain.
The most characteristic feature after 4300 cal. yrs. BP was the enlargement of Piceaabies communities in the coniferous forest belt and Fagus at lower altitudes. However, signs of a gradual decline for Abies are also visible. In the course of the last three millennia, and particularly in historical time, the anthropogenic intervention in the natural vegetation cover resulted in openings in the coniferous forests. Indications of human impact, mainly of pasture activities, are documented by the presence of pollen of Plantagolanceolata, Scleranthus, Artemisia, Cichoriaceae, and grasses. Like in other parts of the Rila Mountain, Piceaabies and Fagus expanded, and the coniferous belt was dominated by Pinuspeuce with admixture of Pinussylvestris, Piceaabies and Abies. Dense communities of Pinusmugo spread on vast areas in the the subalpine belt.
In the area of Lake Suho Ezero Piceaabies rapidly enlarged at 3000 cal. yrs. BP as confirmed by the considerable amount of pollen (zone SE-6, Fig. 41) and macrofossils of needles and seeds (zone MSE-4, Fig. 43). This delayed development of the spruce forests in the Southwestern Rila Mountain can be explained by the ecological requirements of Piceaabies, its competitive relationship with Abies and Fagus, as well as with the location of the main lateglacial refugia.
In historical times the intensification of the anthropogenic impact resulted in destructive changes which mainly affected the coniferous forests, with a decrease for Pinussylvestris, Piceaabies, Pinuspeuce and Abies, and the opening of new areas occupied by herb vegetation (pollen zone SE-7, Fig. 42; pollen zone VP-5, Fig. 48). The thinning of the forest filter promoted an increase in the air-transport of pollen from deciduous trees such as Quercus, Carpinusbetulus, Alnus to higher altitudes. The macrofossil records from Lake Suho Ezero (zone MSE-5, Fig. 43) and from Peat bog Vapsko 1 (Hoevers, 2017) appeared extremely poor in content and only needles of Pinus sp., Pinusmugo/sylvestris, Pinuspeuce and Piceaabies were sporadically determined. The last increase of Fagus and Piceaabies was recorded after 1500 cal. yrs. BP which is in conformity with the general pattern of their Holocene distribution in the Rila Mountain.
The evidence from Lake Vapsko 2 for the last two millennia (pollen zone LV-4, Fig. 51) suggests that Piceaabies slightly expanded while Abies and Fagus declined. The coniferous belt was dominated by Pinuspeuce, Piceaabies, Pinussylvestris and some Abies. The human impact was not very intensive, most probably due to the partial abandonment of the high-mountain pastures in recent times. This resulted in the spread of dense communities of Pinusmugo with Juniperus on vast areas in the subalpine zone in the vicinity of the lake.
Disturbances by fire are among the most important processes that shape forest dynamics and diversity. The first long-term Holocene record of fire regimes in the upper montane forests of the Balkans from the area of Vapski peat bogs was presented, based on macrocharcoal morphologies in combination with pollen-based reconstruction of forest dynamics and fire-related strategies. While biomass burning followed the main trends in climate, the frequency and intensity of fires were strongly linked to fire-related coping strategies of dominant tree taxa (invaders, resisters or avoiders). The invaders are species that are killed by fire but able to penetrate into freshly burned areas (Betula, Alnus, Polypodiaceae, Poaceae and all herbs). The resisters are able to survive surface fires of low to medium intensity (Pinussylvestris/Pinusmugo, Pinuspeuce, Juniperus) and the avoiders include shade-tolerant species easily killed by fire (Piceaabies, Abies). The results indicated 30 fire episodes with a variable temporal distribution over the record, indicative of several distinct fire regime periods. Frequent, low-intensity fire episodes at the termination of the Lateglacial and the beginning of the Holocene between 12000 and 9000 cal. yrs. BP were concurrent with the dominance of invaders (Betula, Alnus, Poaceae, Polypodiaceae). Intermittent occurrence of low- and high-intensity surface and crown fires with longer return intervals between 9000 and 4000 cal. yrs. BP was associated with codominance of resister (Pinussylvestris, Pinusmugo, Pinuspeuce) and avoider (Abies and Piceaabies) forest types. The lengthening of the fire return interval over the past 4000 years was linked to increased abundance of Piceaabies. For the period between 4050 and 2150 cal. yrs. BP a lower biomass burning and small-scale surface fires was registered. A rising number of fire episodes may drive land cover towards more fire-adapted plant communities and less intense fire events with increased dominance of invaders (resprouters that rapidly reach maturity stage) as well as resisters (properties protecting from fire damage) under future warmer and drier climate. This study also showed the potential of combining charcoal morphologies with pollen records to track variability in fire intensity and plant functional attributes over long timescales that are also relevant to forest management stakeholders (Feurdean et al., 2019).
4. PIRIN MOUNTAIN4.1 Physico-geographical characteristics and modern vegetation
Pirin Mountain (peak Vihren, 2914 m) is the third highest on the Balkan peninsula and constitutes part of the vast Rila-Rhodopes massif in Southern Bulgaria. It occupies an area of 2585 km2 between 41°25’-41°55’N and 23°07’-23°53’E in the southwestern corner of Bulgaria, surrounded to the west and east by the valleys of the Struma and Mesta rivers, Rila Mountain to the north and Slavyanka Mountain (peak Gotsev vrah, 2212 m) to the south. The mountain range stretches 70 km in a northwest-southeast direction with an average width of 30-35 km. From a morphographic point of view, the Pirin Mountain is divided into Northern (2914 m), Central (2097 m) and Southern (1974 m) parts. Geologically, Pirin Mountain is a large anticline, its granite centre overlain by Palaeozoic metamorphic rocks (crystalline schist and marble). The northern part occupies 74% of the total area and is composed of granite, crystalline schist and marble. The central part is the smallest in area and is composed of crystalline schist and granite, with marble terrains in the south. The granites predominate in the southern part (Galabov et al., 1977) (Fig. 2). At the beginning of the Quaternary Pirin Mountain was raised several times and denudation plains of different heights and ages were formed, together with steep slopes between them. The best developed denudation surfaces are the ridge and the second one from top to bottom, on which the glacial cirques and the predominant part of the lakes and peat bogs have formed. The discussion on the number of Quaternary glaciations and their characteristics continues (Velchev, 1995, 2020). Most researchers accept the opinion that there is clear evidence to support the idea of two glaciations equitable with the Riss and Würm in the Alps (Lilienberg, Popov, 1966; Popov, 1966; Grünewald, Scheithauer, 2011, etc.). The glaciations were restricted to the Northern Pirin Mountain where typical glacial landforms such as cirques, numerous lakes (119), trough river beds, hanging valleys and moraines were formed on the northeastern slopes. The mountain valley glaciers extended down to c. 1600-1400 m.
Pirin Mountain belongs to the South-Bulgarian climatic region where the sub-mediterranean influence penetrates along the valleys of the Struma and Mesta rivers. Above 1000 m the climate is a typically montane and the mean annual temperature depends on the hypsometric bands. The annual amount of precipitation is 800-1250 mm with a maximum in November-December, much of which is snow above 1500 m. The northwestern winds, 6-10 m/sec prevail, but during winter the frequency of southwestern winds increases (Tishkov, 1976).
The brown mountain-forest (Cambisols) and mountain-meadow soils (Umbrisols) are typical. Dark-colored mountain-forest soils (Humic Cambisols) are widespread within the subalpine belt (Ninov, 1997).
According to the last geobotanical zoning Pirin Mountain is included as a separate region within the Illyrian (Balkan) Province of the European Deciduous Forest Area (Bondev, 2002). The modern vegetation of the mountain resembles a unique combination of central-european, arctic-alpine and mediterranean species. Their distribution in several vegetation altitudinal belts is determined by the contrast between limestone and siliceous areas (Velchev, Tonkov, 1986; Bondev, 1991).
The lowest belt up to 500 m is locally represented only in the southern part of the mountain and consists of communities with mediterranean elements such as Quercuscoccifera, Juniperusexcelsa and Phillyrealatifolia. The xerothermic oak belt (up to 600-700 m) occurs on the western and southern slopes. The dominant species are Quercuspubescens, Quercusfrainetto and Carpinusorientalis, with Paliurusspina-christi and numerous mediterranean and submediterranean herbs. The xeromesophilous oak and hornbeam belt (600-1000 m) is characterized by Quercusdalechampii and Carpinusbetulus with an admixture of Ostryacarpinifolia and Fagussylvatica. Vast areas are occupied by Pinusnigra on the western and northern slopes. The beech belt (1000-1500 m) is fragmented, identified predominantly in the central and southern parts of the mountain by the communities of Fagussylvatica, mixed in some areas with Abiesalba, Pinusnigra and Piceaabies. The coniferous belt (1500-2000 m) is the most compact and well-developed vegetation belt with a diverse flora. On both limestone and siliceous areas grows Pinussylvestris. The Balkan endemic Pinuspeuce and Piceaabies form the upper timber-line in many places. Relict communities of the Balkan subendemic Pinusheldreichii occur exclusively on limestone areas in the northern part. Stands of Abiesalba are also found. The subalpine belt (2000-2500 m) is dominated by thick impenetrable stands of Pinusmugo with Juniperussibirica and Vacciniummyrtillus. Calcareous areas of the alpine belt (2500-2914 m) in the northern part support herb communities of Sesleriacoerulans, Carexkitaibeliana, Dryasoctopetala and the dwarf-willow Salixreticulata, while on siliceous areas Carexcurvula, Agrostisrupestris, Festucaairoides and Empetrumnigrum are common. A characteristic feature of the modern vegetation is the presence of a large group of Balkan and Bulgarian endemics, including 30 local endemics. They are predominantly distributed in the uppermost two vegetation belts and part of them are termed glacial relics. The present-day vegetation in all zones is influenced to a large extent by anthropogenic activities. A large area in the northern part of the mountain, famous for its unique landscape and flora, is protected in the Pirin National Park.
The group of Lakes Banderishki on the Northern Pirin Mountain is situated in a large cirque of the same name. The Banderitsa river derives its water from all 20 lakes in the cirque. Lake Ribno Banderishko is the largest one and is situated at 2190 m (41°44’17.66”N, 23°24’53.86”E) in the subalpine belt. The lake has an elongated shape 384 m long and 230 m wide with a water surface of 6.5 ha. The maximum water depth is 14.2 m. The lake is fed by several upper lakes and its watershed is 3.08 km2 (Figs 3, 53 and 54). The slopes are steep and stony, covered by groups of Pinusmugo and Juniperussibirica within patches of herb vegetation, with the exception of the eastern slope where there is a flat strip 20 m wide (Ivanov, 1964) (Fig. 55).
5B56C340-DA37-549A-ABE6-F44636A21DBC
Map of sites in the Pirin Mountain mentioned in the text: 16. Lake Ribno Banderishko (Tonkov et al., 2002; Tonkov, Possnert, 2021); 17. Lake Muratovo (Bozilova et al., 2004); 18. Peat bog Mozgovitsa (Tonkov, 2003; Marinova, Tonkov, 2012); 19. Peat bog Mutorog and 20. Peat bog Popovi Livadi (Panovska et al., 1995); P. Peat bog Praso (Stefanova, Oeggl, 1993); D. Lake Dalgoto (Stefanova et al., 2003); B. Lake Bezbog (Stefanova, Bozilova, 1995; Stefanova et al., 2006); PE-6. Lake Popovo Ezero-6 (Stefanova, Bozilova, 1995); K-5. Lake Kremensko-5 (Atanassova, Stefanova, 2003; Stefanova et al., 2006).
A view of Lake Ribno Banderishko (Photo: D. Kozuharov).
https://binary.pensoft.net/fig/1672914
<italic>Coring, lithology and radiocarbon dating</italic>
The sediment core 365 cm long was taken from a platform at the central part of the lake at water depth of 8 m with a square-rod piston sampler (Wright, 1991). The lithology of the sediments is: 0-295 cm brown gyttja, 295-325 cm grey silty clay, 325-365 cm grey silt (sand and gravel at 355-365 cm). The radiocarbon age of 8 samples (5 of terrestrial plant macrofossils, 2 of bulk sediment and 1 of chitin from an insect) was determined and the results are shown in Table 14. The age of the sediment core is estimated at c. 14000 cal. yrs. BP (Tonkov et al., 2002; Tonkov, Possnert, 2021).
Radiocarbon dates from Lake Ribno Banderishko.
Lab. code
Depth (cm)
14C age (BP)
14C age cal. BP, ±2σ (mid-point)
Material dated
Ua-14001
45
1340±60
1310-1180 (1245)
Pinus sp. fragments of needles
Ua-13403
150
3800±135
4420-3990 (4205)
Pinuspeuce needle, plant tissue
Ua-12855
155
4270±85
4990-4610 (4800)
chitin part of insect (Otiorhyncus sp.)
Ua-12856
205
5780±110
6720-6470 (6595)
Pinuspeuce shoot
Ua-13404
230
7385±140
8320-8000 (8160)
Pinus sp. needles, budscale of Pinus sp.
Ua-13405
285
9785±360
11750-10350 (11050)
Pinus sp. fragments of needles, Pinuspeuce needle
Ua-61849
290
10331±57
12410-11950 (12180)
gyttja
Ua-61850
320
11030±120
13100-12710 (12905)
silty clay
<italic>Pollen analysis</italic>
Pollen analysis was performed at 5 cm interval and a percentage pollen diagram is constructed (Fig. 56). A separate pollen diagram of the lateglacial section of the core is also presented (Fig. 56a). Pollen accumulation rates (PAR) for the major tree/shrub and herb taxa, complimentary to their percentage values, are also calculated (Fig. 57). On the pollen diagram six local pollen assemblage zones (LPAZs) are recognized (RB-1 to RB-6) (Figs 56 and 57). Brief descriptions are as follows:
3250482F-8650-538E-9785-207217536BFB
Percentage pollen diagram of Lake Ribno Banderishko.
Pollen accumulation rates (PAR; pollen grains cm-2 yr-1) for the main tree/shrub and herb taxa from Lake Ribno Banderishko plotted against age in cal. yrs. BP.
Comparison of the palynostratigraphy and chronology for sites in the Pirin Mountain.
https://binary.pensoft.net/fig/1672919
LPAZ RB-1 (343-317 cm, Artemisia-Pinusdiploxylon-Poaceae-Chenopodiaceae) (~14100-12700 cal. yrs. BP)
The high percentages of herb pollen are attributed to Artemisia 40-60%, Poaceae 20-25%, Chenopodiaceae up to 15%, and a variety of herbs such as Achillea-type, Galium-type, Rumex, Thalictrum, etc. Pollen of trees and shrubs is recorded from Pinusdiploxylon-type 30% (level 330 cm), Betula, Quercus, Alnus, Corylus and Juniperus with minimal values. There are regular finds of Ephedra pollen (distachya-type and fragilis-type). The total PAR of tree taxa is very low up to 250 grains cm-2 yr-1, contributed mainly by Pinusdiploxylon-type 50-220, Juniperus, Betula and Quercus each up to 10. The total PAR of herb taxa is 500-1000, as shown by Artemisia 200-500, Poaceae 100-300 and Chenopodiaceae 200-500.
LPAZ RB-2 (317-293 cm, Artemisia-Poaceae-Pinusdiploxylon-Betula) (12700-11600 cal. yrs. BP)
The steep decline of Artemisia pollen from 55% to 20% is accompanied by a rise of tree pollen reaching 50%, due to Pinusdiploxylon-type 20%, Quercus 15%, Betula 12%, Ulmus 5% and other deciduous taxa. Single pollen grains of Pinuspeuce, Abies and Picea are also recorded. The herb pollen is also dominated by Poaceae 20% and Chenopodiaceae 5%. The total PAR of tree taxa increases slightly up to 450 grains cm-2 yr-1, contributed by Pinusdiploxylon-type 80-160, Juniperus 30, Betula up to 150, Quercus 60, Ulmus 25. The total PAR of herb taxa is 1000-600, attributed to Artemisia 600-100, Poaceae 350 and Chenopodiaceae 175-70.
PAZ RB-3 (293-223 cm, Betula-Quercetum mixtum-Corylus-Poaceae) (11600-7800 cal. yrs. BP)
The total tree pollen curve reaches 65-80%, attributed to Quercus 25%, Corylus up to 30%, Ulmus 15% and Betula 5-10%. Pollen of Pinusdiploxylon-type is 10-15%. The presence of Poaceae drops from 17% to 5% and low values are recorded for Artemisia, Chenopodiaceae, Achillea-type and Galium-type. Slightly higher pollen frequencies are established for Rumex 3-5%, Apiaceae, Filipendula and Cirsium-type. Cyperaceae pollen reaches its maximum of 20% and Polypodiaceae spores are quite abundant up to 10%. The total PAR of tree taxa rises from 500 to 3500 grains cm-2 yr-1, particularly of deciduous trees, contributed by Corylus up to 1250, Quercus 100-750, Ulmus 50-350, Betula up to 100, Pinusdiploxylon-type 750 and Juniperus 50-75. The total PAR of herb taxa is c. 750, attributed to Artemisia up to 100, Poaceae 300-400, Chenopodiaceae up to 100, Rumex 50-70 and Apiaceae 25.
LPAZ RB-4 (223-147 cm, Pinusdiploxylon-Abies-Carpinus-Quercus) (7800-4100 cal. yrs. BP)
The pollen curve of Pinusdiploxylon-type rises steeply to 60%, while the pollen frequencies of Corylus, Quercus and Ulmus decline to 2-5% each. Notable is the establishment of Abies pollen curve and the appearance of Carpinusbetulus and Carpinusorientalis/Ostrya pollen with values c. 5%. At several depths pollen of Fagus, Picea, Vitis and Hedera is recorded. The total PAR of tree taxa reaches 6000-7000 grains cm-2 yr-1, contributed by Pinusdiploxylon-type 4000-5000, Quercus and Ulmus up to 300 each, decline of Corylus to 250, Juniperus 100, Pinuspeuce 40. The increase of Carpinusorientalis/Ostrya and Abies, each up to 400 is worth to be mentioned. The total PAR of herb taxa displays no changes in comparison to the previous zone.
LPAZ RB-5 (147-102 cm, Pinusdiploxylon-Fagus-Abies) (4100-2850 cal. yrs. BP)
This zone is characterized by the establishment of Fagus with 5%. High pollen values are recorded for Pinusdiploxylon-type 55-75%, accompanied by Abies 5-7%, Betula 3% and Alnus. The herb pollen taxa are represented by Poaceae 8-10%, Artemisia up to 7%, Rumex, Ranunculus-type, Plantagolanceolata, and the first finds of Secale and Cerealia-type. The PAR of the main tree taxa displays the following values: Pinusdiploxylon-type 3000-4500 grains cm-2 yr-1, Abies 300-400, Fagusc. 200 with a maximum of 400, Betula 100 up to 250, Picea 100, Pinuspeuce 50-100. The total PAR of herb taxa is 1000-1500, contributed by Poaceae 400-500, Artemisia with a maximum of 350, Rumex up to 200, Apiaceae 100 and Chenopodiaceae 75.
LPAZ RB-6 (102-0 cm, Pinus-Picea-Fagus) (2850 cal. yrs. BP-until present)
Pollen of Pinusdiploxylon-type dominates with 80-90% in the uppermost samples, while Pinuspeuce slightly increases. A characteristic feature is the rise of Picea pollen curve up to 8%. Pollen of Juglans, Vitis and Humulus/Cannabis-type is quite common. The herb pollen taxa are represented by Poaceae, Artemisia, Achillea-type, Ranunculus-type, Caryophyllaceae, Plantagolanceolata, Secale, Cerealia-type, etc. The total PAR of tree taxa keeps values of 3000-6500 grains cm-2 yr-1, attributed to Pinusdiploxylon-type c. 3000-5500, Picea and Fagus each up to 200, Abiesc. 150, Pinuspeuce with a maximum of 175. The total PAR of herb taxa declines, most clearly expressed for Poaceae with c. 200.
Lake Muratovo (site 17)
This lake belongs also to the group of Lakes Banderishki and is located at 2230 m (41°44’44.39”N, 23°24’21.85”E) on a small secondary cirque in the subalpine belt (Figs 3, 53 and 54). The lake has an almost circular shape 133 m long and 114 m wide with water surface of 1.23 ha, a maximum water depth of 3.35 m and watershed area of 0.52 km2. The slopes near the shores are covered by groups of Pinusmugo within patches of herb vegetation (Ivanov, 1964) (Fig. 59).
56B35A51-0628-56C9-BD7C-7F634A339869
A view of Lake Muratovo (Photo: P. Ivanov).
https://binary.pensoft.net/fig/1672920
<italic>Coring, lithology and radiocarbon dating</italic>
Two sediment cores were obtained from a platform at the deepest part of the lake with a square-rod piston sampler (Wright, 1991). The first core PMa is 110 cm long collected at a water depth of 3.15 m. The second core PMb is 185 cm long collected at a water depth of 2.85 m. Both cores stopped at very hard clay material and stones. The sediment lithology is silty clay at the bottom, overlain by clay gyttja, and grey clay at the top. The radiocarbon age of 7 samples of bulk sediment was determined and the results are shown in Table 15. They indicate that the deposition of sediments started c. 4500 cal. yrs. BP which questions the opinion that Lake Muratovo is of glacial origin. Quite probably, the lake was formed either following a tectonic movement or a landslide, after which the accumulation of sediments has become possible (Bozilova et al., 2004).
Radiocarbon dates from Lake Muratovo.
Lab. code
Depth (cm)
14C age (BP)
14C age cal. BP, ±2σ (mid-point)
Material dated
Core PMa
Hela-557
23-25
1695±95
1830-1380 (1605)
clay gyttja
Hela-558
63-65
2365±70
2710-2240 (2475)
clay gyttja
Hela-559
103-105
3800±75
4420-3980 (4200)
clay gyttja
Core PMb
Hela-692
28-30
1215±35
1270-1050 (1160)
clay gyttja
Hela-693
68-70
1885±35
1900-1720 (1810)
clay gyttja
Hela-694
143-150
3485±40
3860-3640 (3750)
clay gyttja
Hela-695
173-175
3915±45
4520-4160 (4340)
clay gyttja
<italic>Pollen analysis</italic>
Pollen analysis was performed at 5 cm interval and for each core a percentage pollen diagram is constructed (Figs 60 and 61). Pollen accumulation rates (PAR) for the main tree/shrub and herb taxa are also calculated for core PMb (Fig. 62). On the pollen diagrams three local pollen assemblage zones (LPAZs) are recognized (PM-1 to PM-3) which are easily correlated (Figs 60, 61 and 58). Brief descriptions are as follows:
EDDEC26C-BB8E-5349-81A6-606B58772135
Percentage pollen diagram of Lake Muratovo (Core PMa).
Pollen accumulation rates (PAR; pollen grains cm-2 yr-1) for the main tree/shrub and herb taxa from Lake Muratovo (Core PMb) plotted against age in cal. yrs. BP.
Pollen of Pinusdiploxylon-type dominates with 50-68% (Fig. 60) and 35-50% (Fig. 61). A characteristic feature are the high pollen values above 20% for Abies. The presence of Pinuspeuce is 5-15%. Pollen grains of Picea, Fagus, Betula and Alnus are each below 5%. Pollen of Quercus, Ulmus, Tilia, Corylus and Carpinusbetulus is of little importance. Single pollen grains of Juglans, Fraxinusexcelsior-type, Acer, Vitis are also recorded. The herb pollen taxa are represented by Poaceae 5%, Artemisia, Cichoriaceae, Achillea-type, Centaureajacea-type, Rumex, Ranunculaceae, Apiaceae and Brassicaceae. In core PMa the quantity of Isoetes spores is higher 2-6% (Fig. 60) compared to the corresponding interval in core PMb (Fig. 61). The total PAR of tree taxa is 5000 to 6500 grains-1 cm-2, contributed mainly by Pinusdiploxylon-type 2000-3500, Abies 1250-1750, Pinuspeuce 500-750, Piceac. 150, and deciduous tree taxa like Fagus, Betula, Alnus, Corylusc.100 each. The total PAR of herb taxa is c. 1000.
The pollen curve of Picea rises to 15-20% in both diagrams. A slight increase for Fagus is accompanied by a decline for Abies. The pollen curve of Pinuspeuce keeps 5-15% as in the preceeding zone. Pollen grains of deciduous trees are rare. The dominant role of Роасеае, Artemisia and Cichoriaceae among the herb pollen taxa continues, together with a slight increase for Chenopodiaceae, Rumex, Polygonumaviculare-type, Scleranthus, Plantagolanceolata. Pollen of Cerealia-type and Triticum-type is also found. The presence of Isoetes spores in core PMa (Fig. 60) declines and in core РМb is 1-5% (Fig. 61). The most characteristic feature is the quick increase of PAR for Picea up to 500 grains-1 cm-2, while the corresponding values for Pinusdiploxylon-type, Pinuspeuce, Fagus, Betula and Corylus are nearly the same like in the previous zone. A gradual decline to 250 is observed for Abies.
The pollen curve of Pinusdiploxylon-type rises to 60-70%. The presence of Pinuspeuce is 15-18%. The participation of Picea decreases to 5-10%, while pollen of Fagus increases slightly to 5-6%. The dominant herb pollen taxa are Poaceae, Artemisia, Achillea-type, Cichoriaceae and Chenopodiaceae. The presence of anthropophytes such as Cerealia-type, Triticum-type, Secale, Polygonumaviculare-type, Plantagolanceolata, Scleranthus and Rumex is permanent. The total PAR of tree taxa increases again to 5500 grains-1 cm-2 with a maximum of 6500 in the uppermost sample, contributed mainly by Pinusdiploxylon-type. The PAR of Picea and Abies rises to 750 each. The total PAR of herb taxa reaches 1500.
Peat bog Mozgovitsa (site 18)
The deep valley of the Mozgovitsa river is located in the central part of the Northwestern Pirin Mountain. It runs about 10 km in east-west direction between 2800 and 1250 m passing through the alpine, subalpine and coniferous belts. The river takes its source from a cirque built up of five tiers with lakes in them. In the lowermost tier, below 1900 m, there are peat bogs formed in depressions and linked by streams of running water (Velchev, Kenderova, 1994). One of these peat bogs, with an area of c. 0.15 ha, located at 1800 m (41°44’21.80”N, 23°25’13.60”E) on the left bank of the river within a thin spruce forest was selected for research (Figs 3 and 53). The steep slopes of the valley are occupied by communities of Betulapendula and Pinussylvestris, mixed in places with Piceaabies and Pinuspeuce. The bog vegetation is composed of Shagnum sp., Carexacutiformis, Carexflava, Carexechinata, Triglochinpalustris, Juncuseffusus, Deschampsiacespitosa, Calthapalustris, Potentillapalustris, Cirsiumappendiculatum, etc. (Tonkov, 2003; Marinova, Tonkov, 2012) (Fig. 63).
15EAE6F6-ACEA-514E-A0AD-1864D55A2008
A view of Peat bog Mozgovitsa (Photo: S. Tonkov).
https://binary.pensoft.net/fig/1672926
<italic>Coring, lithology and radiocarbon dating</italic>
The core 150 cm long was obtained with Dachnowsky hand-corer equipment. The lithology of the sediments is: 0-145 cm peat and 145-150 cm clay with sand. The radiocarbon age of 2 bulk sediment samples was determined and the results are shown in Table 16. The age of the sediment core is estimated at c. 9500 cal. yrs. BP and is correlated with the detailed radiocarbon chronology from Lake Ribno Banderishko.
Radiocarbon dates from Peat bog Mozgovitsa.
Lab. code
Depth (cm)
14C age (BP)
14C age cal. BP, ±2σ (mid-point)
Material dated
Lu-4036
52-68
5700±80
6670-6310 (6490)
peat
Lu-4035
124-136
8040±100
9250-8600 (8925)
peat
<italic>Pollen and plant macrofossil analyses</italic>
Pollen analysis was performed at 5 cm interval and the core was also sampled at 10 cm interval for plant macrofossil analysis. Two fractions of macrofossils after sieving through meshes of 0.4 mm and 0.16 mm were analyzed at magnification 10-40×. Charred wood (> 2 mm) and non-charred (>5 mm) particles were studied under reflected light and light microscopes. Their determination was based on sections in three anatomical plains (transversal, tangential and radial). The plant macrofossils are represented as absolute numbers of determinable items (needles, seeds, nutlets, etc.) per sample volume of 20 ml plotted as histograms on a composite diagram together with the percentage values of the most common pollen taxa. On the diagram five local assemblage zones (LAZs) are recognized (M-1 to M-5) (Figs 64 and 58). Brief descriptions are as follows:
09D38332-9E50-564A-B2C5-04190EAB80BC
Percentage pollen diagram of Peat bog Mozgovitsa with the macrofossils determined.
https://binary.pensoft.net/fig/1672927
LAZ M-1 (150-100 cm, Betula-Quercetum mixtum-Pinus-Carpinus) (9500-7800 cal. yrs. BP)
The pollen samples are dominated by Betula up to 30%, Pinusdiploxylon-type 20% and Quercus up to 30%. Pollen of coniferous (Pinuspeuce, Juniperus, Picea, Abies) and deciduous tree taxa (Carpinusorientalis/Ostrya, Carpinusbetulus, Tilia, Ulmus and Fagus) is continuously recorded. The herb pollen taxa are represented by Poaceae 5-15%, Artemisia, Cichoriaceae, Plantagolanceolata, Ranunculus-type, Apiaceae, etc. Pollen of Cyperaceae reaches 20% and maximal values of 40-45% are recorded for Polypodiaceae spores.
The macrofossil samples are rich in nutlets of Betula. Seeds and needles from conifers (Pinuspeuce, Pinussylvestris/mugo) and in one sample needles of Piceaabies are found. Together with subfossil wood of Pinus sp. charcoal particles are also present. The constituents of the bog vegetation are represented by nutlets of Scirpussylvaticus, fruits of Carex sp., Carexechinata and Carexacuta.
LAZ M-2 (100-80 cm, Betula-Pinus-Abies-Quercus) (7800-7300 cal. yrs. BP)
The pollen curves of Abies and Picea reach 10% and 5%, respectively. Pollen of deciduous trees such as Quercus, Carpinus, Corylus and Betula declines. The transition to the next zone is marked by the quick rise of the pollen curves of Pinusdiploxylon-type and Pinuspeuce. The variety of herb pollen taxa remains like in the previous zone.
The macrofossil record is dominated by nutlets of Betula which subsequently disappear. Subfossil wood of Salix and Alnus is also found. A substantial increase in the presence of fruits/nutlets of various Carex species, Scirpussylvaticus and Juncuseffusus-type is observed.
LAZ M-3 (80-50 cm, Pinus-Abies) (7300-4800 cal. yrs. BP)
Pollen of Pinusdiploxylon-type 50% and Pinuspeuce 28% reaches maximal values, while Abies and Picea are represented with 5-10% each. Pollen of various deciduous tree taxa is below 3%.
The macrofossil record comprises needles and seeds of Pinuspeuce, Pinussylvestris/mugo and Pinus sp. Nutlets of Carex sp., Carexacuta, Carexechinata and Juncuseffusus-type are also determined.
LAZ M-4 (50-28 cm, Pinus-Abies-Picea) (4800-2800 cal. yrs. BP)
Alongside with the steady presence of Pinusdiploxylon-type and Pinuspeuce pollen, a slight increase for pollen of Picea, Abies, Juniperus, Betula and Carpinusbetulus is established. Pollen grains of Juglans are also determined. The total quantity of herb pollen starts to increase.
Wood and needles of Piceaabies, as well as wood of Pinus sp., Salix, Juniperus, needles and seeds of Pinuspeuce are found. Nutlets of various Carex species are present in the fossil record.
In the uppermost samples pollen of Picea with 13% and Fagus with 5% reaches maximal values. Pollen of Pinusdiploxylon-type is c. 40%, while Pinuspeuce declines to 6-10%. Higher pollen frequencies are recorded for Poaceae 20-23%. The anthropogenic pollen indicators are represented by Urtica, Rumex, Plantagolanceolata, Cerealia-type. Pollen of Cyperaceae is 25%.
The macrofossil record is dominated by needles and wood of Piceaabies, scattered finds of wood of Pinus sp., Juniperus and Salix. Nutlets and fruits of Carexechinata, Carexcanescens and Carexacuta are determined.
4.3 Vegetation history in the Northern Pirin MountainLateglacial
The core from Lake Ribno Banderishko is the pioneer continuous postglacial sequence from the Pirin Mountain. It spans most of the Lateglacial and the entire Holocene, thus providing an opportunity to reconstruct high altitudinal vegetation and climate changes in the northern part of the mountain. The pollen stratigraphy of the lateglacial section reveals the vegetation changes for the time period 14000-11600 cal. yrs. BP (pollen zones RB-1 and RB-2; Fig. 56a). The oldest pollen zone RB-1, which covers the time window 14000-12750 cal. yrs. BP, can be related to the lateglacial interstadial complex Bölling/Alleröd. The high values of herb pollen taxa with the dominance of Artemisia, Poaceae and Chenopodiaceae imply the existence of treeless “mountain-steppe” vegetation composed of cold-tolerant and heliophilous species. Stands of pines (Pinusmugo, Pinussylvestris and few Pinuspeuce), Betula and shrubland of Juniperus, and Ephedra, thrived in sheltered places in the vicinity of the lake. Both Ephedra species, indicative of the lateglacial mountain flora, probably occupied open base-rich places but later on these plants disappeared from the flora of the Pirin Mountain like in the Rila Mountain. In the paleovegetation reconstruction it needs attention that the pollen grains produced by the Balkan subendemic Pinusheldreichii fall within Pinusdiploxylon-type group. Unfortunately, it is not possible to estimate the proportion of Pinusheldreichii in the total quantity of pine pollen recorded. Evidently, this tree was present far from the lake at lower altitudes, bearing in mind that its present-day distribution is below 1800 m. The occurrence of deciduous tree pollen from Quercus, Ulmus, Corylus, and Carpinus, though in low quantities, suggests that these trees survived the harsh lateglacial conditions in places where moisture, humidity and soils appeared sufficient for their growth.
The time interval 12750-11600 cal. yrs. BP (pollen zone RB-2) can be chronologically correlated with the last climatic reversal, the Younger Dryas stadial. The “mountain-steppe” herb vegetation continued to dominate until c. 12200 cal. yrs. BP and afterwards it was partly replaced for a short period of time by stands of Pinus, Betula and Juniperus. A signal for climate improvement resulted in the spread of mixed oak forests from their refuges at low altitudes and the appearance of moisture-demanding trees and climbers such as Abies, Picea, Fagus and Vitis. Quite probably, populations of fir, spruce and beech were present during the Lateglacial in refuges on the Pirin Mountain. After this short-term climate improvement, typical lateglacial conditions returned in the highest parts of the mountain and the tree stands moved down along the mountain slopes. The PAR of plant taxa during the Lateglacial confirms the proposed vegetation reconstruction as shown by the rather low pollen influxes of trees and the higher values of herbs (Artemisia, Poaceae, Chenopodiaceae) (Fig. 57).
Other studies of lateglacial sites from the Northern Pirin Mountain complement the picture of vegetation and climate changes (Fig. 53). Sediments of lateglacial age consisiting of 20 cm grey silt, not radiocarbon dated, from Lake Dalgoto located at 2310 m above Lake Ribno Banderishko (Fig. 54), were assigned to the stadial Younger Dryas on the basis of their palynostratigraphy. It indicated the existence of open xerophytic herb vegetation with Artemisia, Chenopodiaceae, together with species of the Asteraceae (Achillea, Aster, Centaurea), Caryophyllaceae (Dianthus, Silene), Apiaceae, Ranunculaceae and Brassicaceae. At the termination of the Lateglacial are recorded increasing values of tree taxa (Pinusdiploxylon-type, Quercus and Betula) and strong decrease of Artemisia and Chenopodiaceae (Stefanova, Ammann, 2003).
The core of Lake Kremensko-5 located at 2124 m (Fig. 53) yielded sediments from more than 13500 14C yrs. BP and a pollen stratigraphy that can be correlated with the interstadial/stadial cycle of the Lateglacial. The radiocarbon date of 16000 cal. yrs. BP points to a stadial phase that can be correlated with the Oldest Dryas. The climate amelioration during the interstadial is confirmed by the higher importance of tree taxa, leading to enlargement of the coniferous woods around the lake at 14420 cal. yrs. BP. The upper part of the lateglacial record of Lake Kremensko-5 remained without absolute age determination, but the Younger Dryas stadial c. 25 cm in thickness is delimited on the basis of the dominance of Artemisia, Chenopodiaceae and other various characteristic herb taxa, and the occurrence of the Juniperus-Ephedra assembalges (Atanassova, Stefanova, 2003).
Later studies in the Northern Pirin Mountain attempted to provide a chronological framework for the Lateglacial based on new pollen and plant macrofossil sequences recovered from Lake Kremensko-5 and Lake Bezbog located at 2250 m (Fig. 53). The reconstruction of the lateglacial vegetation presented a wide distribution and dominance of Artemisia-Chenopodiaceae-Poaceae with Ephedra shrubland at higher altitudes during the Oldest Dryas. Subsequently, the Bölling/Alleröd interstadial was characterized by the spread of Pinus (Pinuspeuce, Pinusdiploxylon-type) and Juniperus with a partial retreat of the herb vegetation in the conditions of a milder climate. The palynostratigraphy for the Younger Dryas stadial featured a re-advance of the herb vegetation and the presence of several trees and shrubs such as Betulapendula, Pinuspeuce and Juniperussibirica was confirmed by macrofossils finds. Following the depth-age models constructed and the changes in biostratigraphy, the identification of the Bölling/Alleröd interstadial between 13800 and 12600 cal. yrs. BP at Lake Bezbog, and between 14100 and 12600 cal. yrs. BP at Lake Kremensko-5, was correlated with the Greenland Interstadial GI-1. The proposed lower boundary of the interstadial differs considerably from the ice-core records which might be explained either by a time-lag in the vegetation response or certain disadvantages of the depth-age models due to the still insufficient number of radiocarbon dates. For the Younger Dryas stadial, when the final reversal of the typical lateglacial conditions has occurred, a radiocarbon date of 11920 cal. yrs. BP was obtained from Lake Bezbog (Stefanova et al., 2006).
All lateglacial pollen sequences analysed indicated that the vegetation type characteristic of localities at mid-high altitudes could be defined as “mountain steppe-forest”. Most probably, at lower elevations the ecological conditions favored the survival in refuges of populations of various thermophilous trees and shrubs with their subsequent vertical migration in the Holocene. The available evidence supports the hypothesis that the Balkans served as one of the main refugial areas in Southern Europe (Huntley, Birks, 1983; Bennett et al., 1991; Lang, 1994; Tzedakis, 2004; Lang et al., 2023, etc.).
The Holocene
The onset of the Holocene after 11600 cal. yrs. BP is manifested by a rise in the total tree pollen, namely contributed by deciduous trees (pollen zone RB-3, Fig. 56). A period of dynamic changes in the vegetation cover started in response to rapid climate amelioration. There was a noticeable decline in the “mountain-steppe” vegetation composed of species of Poaceae, Artemisia, Chenopodiaceae, Achillea, Galium. The remnants of this vegetation were replaced by species-rich herb pioneer communities of Apiaceae, Filipendula, Ranunculaceae, Caryophyllaceae, Brassicaceae and Helianthemum. The reforestation started with the spread of Betula accompanied by Juniperus and Alnus. It is likely, that birch and pines (Pinussylvestris, Pinuspeuce) formed the upper timber-line in the Early Holocene. The determination of fragments of needles from Pinus sp. (Pinusmugo and/or Pinussylvestris) and Pinuspeuce in the sediments of Lake Ribno Banderishko (Table 14) supports this assumption. On the other hand, reliable information on the proximate position of the timber-line can only be obtained after a detailed macrofossil analysis is performed. A comparison with the Early Holocene plant macrofossil record from Lake Suho Ezero on the Southwestern Rila Mountain (Fig. 43) reveals an abundance of fruit/bud scales of Betula and sporadic finds of Pinuspeuce and Pinus sp. needles, suggesting that the timber-line was passed around 1900 m altitude. It is logical to assume that the position of the timber-line on the Northern Pirin Mountain did not differ much from the situation on the Rila Mountain.
The palynological record from Lake Ribno Banderishko implies that mixed oak forests with abundant Ulmus, less Tilia, and some Acer and Fraxinusexcelsior, reached their maximal distribution in the lower parts of the mountain c. 10000-9000 cal. yrs. BP. Later on, Corylus expanded and became widespread c. 8500-8000 cal. yrs. BP. The presence of climbers such as Vitis and Hedera in the deciduous forests indicates an increase of humidity and a rise in the mean annual temperature.
Around 9500 cal. yrs. BP the paleoecological evidence comprising pollen and plant macrofossils from the Peat bog Mozgovitsa reveals that the primary role in the initial phase of afforestation was taken by Betula that occupied large areas, together with groups of pines (Pinussylvestris, Pinuspeuce, Pinusmugo), Juniperus, Alnus and Salix (zone M-1, Fig. 64). Birch as a pioneer tree invaded barren soils and gradually formed the upper timber-line. Below the birch forests with stands of pines, deciduous oak forests with Ulmus, Tilia, Acer, Corylus and Carpinus started to expand. The relatively high values of deciduous tree pollen recorded presume an easier pollen transport upslope. Hazel, like birch, appeared as a pioneer element on open areas prior to the other trees. Natural fires were also quite common as indicated by the presence of macro-charcoal fragments, some of them identified as from Pinus sp. In addition, oak macrofossils found in the Northeastern Pirin Mountain at Peat bog Praso located at 1900 m (Fig. 53) as much as 800 m above the present range of oak (Stefanova, Oeggl, 1993) demonstrate that the temperate forests reached higher elevations during the Early Holocene, perhaps in response to the warmer summer conditions (Wright et al., 2003).
The Early Holocene pollen assemblages from Peat bog Mozgovitsa contain also minor, but steady quantities of pollen of mesophilous trees such as Abies, Fagus and Picea. The needles of Piceaabies dated to 9000 cal. yrs. BP are the oldest ones, established so far, from the mountains in Bulgaria (zone M-1, Fig. 64). These records imply that groups of the above-mentioned moisture-demanding trees survived in environmentally favourable habitats like the deep mountain valley of the Mozgovitsa river. This is not unexpected as part of the lateglacial pollen record from Lake Ribno Banderishko contains pollen of trees and climbers like Abies, Picea, Fagus and Vitis (Fig. 56a).
The vegetation development after 7800 cal. yrs. BP was characterized by important changes in forest composition (pollen zone RB-4, Fig. 56; zone M-2, Fig. 64). The rapid decline of pollen and plant macrofossils from Betula indicates that birch forests retreated and at many places had given way to the coniferous vegetation. The vertical migration of the conifers and the enlargement of their area were facilitated by the formation of humus rich soils and increase in precipitation and humidity (Bennett, Willis, 1995; Davis et al., 2003). Such favorable climatic and edaphic conditions initiated the formation of a coniferous belt dominated by Pinussylvestris, Pinuspeuce, Abiesalba, while communities of Pinusheldreichii and Pinusnigra spread on calcareous areas. At the same time in many areas the mixed deciduous forests were replaced by Carpinusorientalis/Ostryacarpinifolia, and by Carpinusbetulus. The appearance of Carpinusorientalis/Ostrya pollen is indicative of the establishment of sub-mediterranean conditions in the foothills of the Pirin Mountain after c. 7500 cal. yrs. BP.
The results of plant macrofossil analyses from other sites on the Northern Pirin Mountain after 7500 cal. yrs. BP show the appearance of needles of Pinuspeuce, bud-scales and microsporophylls of Pinus sp. in the surroundings of Lake Popovo Ezero-6 located at 2185 m (Fig. 53) (Stefanova, Bozilova, 1995). An abundance of needles and seeds of Pinuspeuce, needles of Abiesalba, bud-scales and microsporophylls of Pinus sp. was recorded in the sediments of the Peat bog Praso (Stefanova, Oeggl, 1993). This evidence suggests that during the Holocene climatic optimum the timber-line on the Northern Pirin Mountain reached its maximum height compared to the present-day situation.
The palynological data from Lake Muratovo c. 4600 cal. yrs. BP presents a wide distribution of coniferous forests, not far away from the lake, composed of Pinuspeuce, Pinussylvestris, Abiesalba, and quite probably Pinusheldreichii (Figs 60 and 61). Groups of Pinusmugo and Juniperus within the herb vegetation dominated by Poaceae species, and various representatives of Ranunculaceae, Brassicaceae, Apiaceae, Caryophyllaceae, thrived in the subalpine zone above the timber-line. Along mountain brooks stands of Alnus spread and on poor soils on steep stony slopes Betula was growing as a pioneer tree. Possibly, by that time, isolated localities with sufficient moisture sheltered small populations of Piceaabies and Fagus.
It is important to point out that the time interval 4300-3700 cal. yrs. BP is linked to the final phase of the wide distribution of Abiesalba in the coniferous forests that existed since 7900 cal. yrs. BP. Around 3000/2800 cal. yrs. BP a decrease in the participation of fir is observed due to the increasing occurrence of spruce. Meanwhile, the dense coniferous forests acted as a filter for the airborne upslope transport of deciduous tree pollen of Quercus, Ulmus, Tilia, Carpinus and Corylus from lower altitudes.
The spread of Fagus on the Northern Pirin Mountain started at 4400 cal. yrs. BP (pollen zone RB-5, Fig. 56), although this tree was established at low altitudes rather earlier c. 8000 cal. yrs. BP (zone M-1, Fig. 64). Beech formed either pure or mixed stands with Abiesalba, and grew partly with Carpinusbetulus in place of other deciduous trees, predominantly on north-facing slopes. Around 4500-4000 cal. yrs. BP beech started to become an important constituent of the forest cover in almost all Bulgarian mountains, and subsequently expanded in Subatlantic time (Filipova-Marinova, 1995).
Over several millennia Pinussylvestris, Pinuspeuce, and partly Abiesalba, were the main constituents of the coniferous belt in the Mozgovitsa river valley. Spruce was still less abundant in these forests (Fig. 64), but the slow increase in its pollen frequencies in the entire study area signalled that it has started to gain importance after c. 4600 cal. yrs. BP (pollen zone RB-5, Fig. 56; pollen zone PM-1, Figs 60 and 61).
Later on, after 2800 cal. yrs. BP, Piceaabies invaded new areas and shaped the timber-line at many places, solely or with Pinussylvestris and Pinuspeuce. As a main reason for this event a change of climate with lower temperatures and higher precipitation is considered likely in the temperate regions, synchronous with an abrupt increase in radiocarbon in the atmosphere c. 850 cal. BC as a result of increased solar activity (van Geel et al., 1998).
The reasons for this late establishment and subsequent expansion of spruce are still debatable and are most probably of complex character. The rather late Holocene arrival of spruce in the high central montane parts of the Balkan peninsula, Rila and Pirin mountains included, has led to the idea that the closest refugial areas for Piceaabies from where it migrated at a slow rate to the south and southeast were located in the northernmost parts of the Balkan peninsula - Southeast Alps, Dinaric Mountains and Carpathian Mountains (Lang 1994; Farcas et al. 1999; Björkman et al. 2003; Latalowa, van der Knaap, 2006). The hypothesis that local refuges with residual populations of spruce could have also existed in isolated interior montane areas of the peninsula with sufficient moisture, also deserves attention (Ravazzi, 2002; Tonkov, 2003).
It should be pointed out that competition with other trees, notably Abies, was the main factor accounting for reduced migration rates of Picea after the mid-Atlantic in forest communities in the French Alps (Beaulieu et al., 1994). Such a tendency is also recorded in the pollen diagrams from Lake Muratovo. The estimated age when spruce became one of the dominant trees in the coniferous belt is in good agreement with other palynological studies from the Northern Pirin Mountain (Bozilova, 1975, 1986; Stefanova, Oeggl, 1993; Stefanova, Bozilova, 1995; Stefanova et al., 2006).
In the sediments from Peat bog Mozgovitsa the rise of Picea pollen curve is preceded by an increase of Artemisia, Poaceae and other herbs. A characteristic feature is the abundance of macrofossils from Piceaabies such as needles and charred wood, and occasional finds of seeds of Pinus sp., needles and seeds of Pinuspeuce, and subfossil wood of Pinus sp., Juniperus, Salix and charred wood of Pinus. Seeds and nutlets of Teucriummontanum, Ranunculusnemorosus point to the existence of mountain meadows, and those of Potentillapalustris, Carex and Eriophorum species originated from the local vegetation of the peat bog (zones M-4 and M-5, Fig. 64). A comparison with the palynological and plant macrofossil results obtained from Late Holocene peat profiles, located between 1600 and 2000 m in the adjacent Begovitsa river valley, confirms that after c. 2200 cal. yrs. BP deforestation in the coniferous belt resulted in the lowering of the upper timber-line and the appearance of new pasture land (Bozilova et al., 2002). The occurrence of charcoal particles, wood of Piceaabies and Pinus sp., and the regular presence of pollen of anthropophytes suggests human induced fires. The basic means of livelihood of the native population was animal husbandry, including livestock-grazing in the high-mountain pastures. Even nowadays remains of old sheep pens are visible on the river terraces.
Likewise, after c. 1750 cal. yrs. BP the vegetation development holds the features of an enhancing anthropogenic activity, although traces of early human impact may have been detected even earlier, during the Late Bronze Age and Hellenistic periods (pollen zones PM-2 and PM-3, Figs 60 and 61). The increasing values of Rumex, Plantagolanceolata, Scleranthus and some Asteraceae pollen indicate the existence of seasonal subalpine pastures, trampling and ruderal communities. The pollen grains of Cerealia-type, Triticum-type and Secale testify to agricultural activity in the mountain foothills.
At many places in most recent times after 900 cal. yrs. BP Pinuspeuce and Piceaabies shaped the upper timber-line, while Pinusmugo spread in the subalpine zone (pollen zone RB-6, Fig. 56; pollen zone PM-3, Figs 60 and 61). Clear indications of human activity at lower altitudes and expansion of agriculture are connected with finds of pollen of Cerealia-type, whereas the pollen frequencies of Scleranthus, Rumex and Plantagolanceolata suggest livestock-grazing in the high-mountain pastures. The presence of Juglans pollen also testifies to the existence of settlements on the mountain foothills where walnut was cultivated. The decline in the pollen frequencies of almost all tree taxa, with the exception of Pinus, presumes pronounced human interference in all vegetation belts during the last centuries.
The patterns of the vegetation dynamics in the Northern Pirin Mountain (Fig. 58) appear quite similar to those established for the Rila Mountain (Fig. 7) and future paleoecological investigations of lake and peat bog sediments in this area will provide further details on the environmental changes in postglacial time.
4.4 Southern Pirin Mountain – Study sitesPeat bog Mutorog (site 19)
This peat bog is located at 1700 m in northeast direction from Mutorog peak in a forest of Piceaabies with an admixture of Pinussylvestris, Abiesalba and Pinuspeuce. The bog vegetation is composed of Carexleporina, Carexflava, Carexstellulata, Nardusstricta, Deschampsiacespitosa, Potentillapalustris, Geumcoccineum, Galiumpalustris, Saxifragarotundifolia, etc. (Panovska et al., 1995) (Fig. 53).
<italic>Coring, lithology and radiocarbon dating</italic>
The core 110 cm long was collected with Dachnowsky hand-corer equipment. The lithology of the sediments is: 0-30 сm peat, 30-35 сm sand, 35-45 сm peat, 45-55 сm peat with sand, 55-65 сm peat, 65-80 сm peat with sand, 80-90 сm peat and 90-110 сm peaty gyttja. The radiocarbon age of one bulk sediment sample was determined and the result is shown in Table 17. The age of the sediment core is determined at 3500 cal. yrs. BP.
Radiocarbon dates from Peat bog Mutorog and Peat bog Popovi Livadi.
Lab. code
Depth (cm)
14C age (BP)
14C age cal. BP, ±2σ (mid-point)
Cal. BC/AD (mid-point)
Material dated
Mutorog
KL-3416
90-110
3240±120
3830-3170 (3500)
1880-1220 (1550) BC
peaty gyttja
Popovi Livadi
Hv-17896
80-100
1400±90
1530-1090 (1310)
420-860 (640) AD
peat
Hv-17895
250-270
2610±70
2870-2470 (2670)
920-520 (720) BC
peaty gyttja
<italic>Pollen analysis</italic>
Pollen analysis was performed at 10 cm interval and a percentage pollen diagram is constructed (Fig. 65). On the pollen diagram two local pollen assemblage zones (LPAZs) are recognized (MT-1 and MT-2). Brief descriptions are as follows:
The total tree pollen prevails with 45-70%, attributed to Fagus 27-37%, Corylus 20-10%, Tilia 10% аnd Carpinusorientalis/Ostrya 15%. Pollen of Pinusdiploxylon-type is present with 5-17%, Juniperus and Pinuspeuce each with 2-4%. The participation of Picea and Abies is insignificant. The herb pollen taxa are represented by Poaceae 22-10%, Cichoriaceae, Achillea-type and Scleranthus each with 3-7%, etc. Spores of Polypodiaceae 35-45% are also found.
LPAZ MT-2 (63-0см, Pinusdiploxylon-Quercus-NAP)
The dominant pollen type is Pinusdiploxylon with 50-60%. The presence of Quercus, Fagus, Pinuspeuce, Alnus, Corylus, Abies, Juniperus pollen is each with 3-7%. In the uppermost sample Picea reaches 13%. The pollen curve of Poaceae displays a maximum of 30% (level 30 cm) and then declines to 3-5%. The variety of herb pollen taxa is considerable. The presence of Achillea-type, Cichoriaceae, Plantagolanceolata, Scleranthus, Hordeum-type and Cyperaceae pollen is worth to be mentioned.
Peat bog Popovi Livadi (site 20)
This peat bog is located at 1430 m (41°32’55.24”N, 23°38’24.34”E) in a large depression. It borders to the south a forest of Pinussylvestris with an admixture of Piceaabies and Abiesalba. The understory is composed of Juniperuscommunis, Juniperussibirica, Vacciniummyrtillus. On the steep northern slopes of the area an inverse distribution of beech above the coniferous communities is observed. The bog vegetation is composed of Sphagnum sp., Carexrostrata, Carexhirta, Carexcanescens, Carexacuta, Juncuscompressus, Juncusalpigenus, Eriophorumvaginatum, Eriophorumlatifolium, Luzulanigricans, Deschampsiaflexuosa, Deschampsiacespitosa, Geumcoccineum, Cardaminepalustris, Veronicascutellata, Menyanthestrifoliata, Calthapalustris, Potentilla.palustris, etc. (Panovska et al., 1995) (Fig. 53).
<italic>Coring, lithology and radiocarbon dating</italic>
The core 290 cm long was collected with Dachnowsky hand-corer equipment. The lithology of the sediments is: 0-30 сm slightly decomposed Sphagnum peat, 30-100 сm peat, 100-110 сm peaty gyttja, 110-230 сm peat, 230-270 сm peaty gyttja, 270-290 сm peat with sand. The radiocarbon age of 2 bulk sediment sample was determined and the results are shown in Table 17. The age of the sediment core is determined at c. 3000 cal. yrs. BP.
<italic>Pollen analysis</italic>
Pollen analysis was performed at 10 cm interval and a percentage pollen diagram is constructed. Three local pollen assemblage zones (LPAZs) are recognized (PL-1 to PL-3) (Figs 66 and 58). Brief descriptions are as follows:
F6688AF8-E5A8-5680-A8D3-D2FD13846A49
Percentage pollen diagram of Peat bog Popovi Livadi.
The total tree pollen dominates with 60-80%, contributed by Pinusdiploxylon-type 20-30%, Abies up to 20%, Fagus up to 20%, Quercus 5-18%. The presence of Pinuspeuce, Picea, Juniperus, Salix and Ulmus is insignificant. The herb pollen taxa are represented mainly by Poaceae 10-20%, Cichoriaceae, Achillea-type, Rumex and Ranunculaceae each with 2-4%. Local maxima are recorded for spores of Polypodiaceae 60-80% and Equisetum 40%.
This zone is well defined by the ratio АР/NAP=40/60%. Pollen of Pinusdiploxylon-type is below 10%, Juniperus 3-8%, Betula 3-7%, Quercus 10-15% and Fagus 5-7%. The variety of herb pollen taxa is high represented by Poaceae up to 37%, Scleranthus 19%, Hordeum-type 10-15%, Rumex 12%, Artemisia, Brassicaceae, Ranunculaceae, Plantagolanceolata, etc.
LPAZ PL-3 (95-0 см, Pinusdiploxylon-Fagus) (1300 cal. yrs. BP-until present)
Pollen of Pinusdiploxylon-type dominates with 60-80%. A local maximum is registered for Fagus 10-12%, while Picea and Abies are present each with 1-3%. The pollen curve of Quercus declines to 2-4%. Among the herb pollen taxa Poaceae participates with 5-10%. In several samples local maxima are established for Scleranthus 10%, Plantagolanceolata 35%, Hordeum-type 5%, Cyperaceae 80% and spores of Sphagnum 220%.
<italic>Plant macrofossil analysis</italic>
The core was also sampled at 10 cm interval for determination of plant macrofossils. The results are presented on a macrofossil diagram in absolute numbers for flowers, fruits and needles, while the occurrence of wood is indicated by dots (Fig. 67). Three local macrofossil assemblage zones (LMAZs) can be recognized (MPL-1 to MPL-3). Brief descriptions are as follows:
F81DD2C7-77E0-51DD-8D91-EF305F12E223
Plant macrofossil diagram of Peat bog Popovi Livadi.
https://binary.pensoft.net/fig/1672932
LMAZ MPL-1 (290-245 сm)
Macrofossils from tree taxa are quite common such as Abiesalba (wood, needles), Carpinusbetulus and Corylus (wood), Carpinusorientalis (fragments of leaves), Fagus (wood, flowers). All these finds were extracted from the sample radiocarbon dated at 2610±70 C14 yrs. BP (2670 cal. yrs. BP). Fruits of Potentillapalustris, Potentilla sp., Ranunculus and Carex sp. are found.
LMAZ MPL-2 (245-135 сm)
Macrofossils from tree taxa are absent. In the lower part of the zone fruits of Carex sp. are abundant. Fruits of Potentilla sp., Menyanthestrifoliata, Chenopodiumalbum are also determined.
LMAZ MPL-3 (135-0 сm)
Charred wood is found in almost all samples and a seed of Pinussylvestris. Fruits of Carex sp., Menyanthestrifoliata, Potentilla sp. and Potentillapalustris are established.
4.5 Vegetation history in the Southern Pirin Mountain
The pollen diagrams and the plant macroremains reflect the changes in the vegetation cover over the last c. 3500 years. The paleoecological data from the two peat bogs and the periods of increased anthropogenic activities correlate very well, supported by the radiocarbon dates.
In the area of Peat bog Mutorog the spread of almost pure Fagus communities started at c. 3500 cal. yrs. BP and deciduous trees such as Tilia, Corylus and Ulmus retreated at lower altitudes. The participation of Pinus (most probably Pinussylvestris) was negligible like that of Abies, while on more open terrains were found groups of Betula.
In the vicinity of Peat bog Popovi Livadi mixed Abies-Fagus forests were present, proved by the find of macroremains (needles, wood and flowers). Corylus and Carpinusorientalis were also growing as confirmed by the determination of fossil wood. The pollen grains from Ephedrafragilis-type suggest long-distant air transport but do not rule out the possibility that Ephedra was occurring in the eastern parts of the Southern Pirin Mountain by that time (pollen zone PL-2, Fig. 66). After 2700 cal. yrs. BP the forests were destroyed to a large extent in the more easily accessible places.
There is strong evidence of anthropogenic interference in the Popovi Livadi area between 2100 and 1300 cal. yrs. BP. The flat land surrounding the peat bog has proven to be suitable for practicing mountain farming with cultivation of Hordeum and Secale as well as for animal husbandry. The presence of pollen indicators for grazing, ruderal communities and forest paths such as Scleranthus, Rumex, Plantagolanceolata, Juniperus and some Asteraceae species exceeds significantly the amount of pollen from cultivated cereals for a long period. This confirms that the area was extremely suitable for grazing since early historical times.
It was difficult for the local population to exploit the beech forests on the steep slopes above 1000-1500 m and this was probably one of the reasons for the recent inverse distribution of fragments of beech forests over the coniferous forests in this part of the mountain.
A significant change in the composition of the forest vegetation is visible after 1300 cal. yrs. BP (VIII-th cent. AD) when the anthropogenic influence in the area weakened and a large part of the land used by humans was abandoned. This led to the enlargement of forests of Pinussylvestris and some restoration of Fagus communities.
The last tree species that permanently settled in many places after 700 cal. yrs. BP (XIII-th cent. AD) was Piceaabies. The subsequent presence of spruce in this part of the mountain in the altitudinal zone between 1400 and 1700 m like in the Northern Pirin Mountain and in the Rila Mountain can be associated with changes in the climate conditions during the Little Ice Age.
5. WESTERN RHODOPES MOUNTAIN5.1 Physico-geographical characteristics and modern vegetation
The Rhodopes Mountain is a large massif, approximately 240 km W-E and 100 km N-S, which occupies 14730 km2 in Southern Bulgaria and 3270 km2 in Northern Greece (Fig. 2). It is divided into the Western Rhodopes (8732.1 km2) with the highest peak Goljam Perelik (2191 m) characterized by vast level stretches that are most prominent in the interior parts at 1500 m in the area of Shiroka Polyana, and the Eastern Rhodopes (1463 m) with its wide valleys and short ravines. The typical wide valleys in the Western Rhodopes are crossed by numerous small streams with narrow beds meandering downslope. These valleys provided favorable conditions for the formation of large peatland complexes. Most of them were destroyed during the construction of artificial reservoirs in the 1950s. Geologically, the core of the mountain is a large granite pluton covered by metamorphic rocks (gneisses, schists and marble) of Paleozoic and pre-Paleozoic ages. The contemporary relief of the Western Rhodopes was shaped during the Neogene-Quaternary when the rising vault was broken into large blocks by numerous faults. Some of these blocks subsided and formed intermontane structural basins (Galabov et al ., 1977). During the Quaternary the mountain was not glaciated but the highest parts above 2000 m were under the influence of periglacial processes (Vlaskov, 2002 ).
The climate of the Western Rhodopes Mountain is a montane variant of the Transitional Continental type. The mean annual air temperature is 5°С-10°С at 1000 m with mean January temperatures below 0°С, while the mean July temperature depends on the altitude. The mean annual precipitation is 600-800 mm with a maximum in May-June and a minimum in August-September. The Mediterranean influence is more clearly expressed in the southern parts. The northern slopes of the mountain are in a precipitation shadow and the amount of annual precipitation is less than in the interior parts (Velev, 2002).
The ba sic soil types are mountain-brown forest (Cambisols, 60%) up to 1700-1900 m, cinnamomic forest (chromic Cambisols) up to 800 m, humic-carbonate (rendzic Leptosols), and mountain-meadow (Umbrisols) on the highest parts (Ninov, 1997).
Accord ing to the most recent geobotanical zoning of the country (Bondev, 2002) the Western Rhodopes Mountain is recognized as a separate region characterized by vast distribution of coniferous forests dominated by Piceaabies and Pinussylvestris with an admixture of Abiesalba, Fagussylvatica, Betulapendula and Pinuspeuce in some places. The deciduous forests occupy areas at lower altitudes predominantly in the eastern and northern parts. They are composed mainly of Quercusdalechampii with occasional presence of Quercusfrainetto and Quercuscerris on south-facing slopes. Mixed forests of Quercusdalechampii, Fagussylvatica, Carpinusbetulus with participation of Ostryacarpinifolia occur in the valleys. Above the oak vegetation belt, beech forests grow mixed with Acerpseudoplatanus, Populustremula and Abiesalba on north-facing slopes. Quite often mixed coniferous-deciduous communities are also found. The present-day vegetation composition in many places has been influenced by anthropogenic impact, including grazing herbivores, cultivation of potatoes and crops, timber production, construction of reservoirs on the place of former bogs and fens, and more recently, by an increase in the intensity of touristic activities (Tonkov et al., 2014) .
5.2 Study sitesMire Kupena (site 21)
This mire is a former lake at 1356 m (41°59'07.5”N, 24°19'05.1”E) found on the territory of the Biosphere UNESCO Reserve Kupena in the Western Rhodopes Mountain (Fig. 3). The reserve is located close to the town of Peshtera between 600 and 1400 m on a north-facing slope and occupies an area of 1759.2 ha. It was declared for protection of the natural landscape and wild flora and fauna (Velev et al., 2015). Its pre sent vegetation is rather diverse. The lower parts are dominated by plant communities of Quercusdalechampii mixed in some places with Carpinusbetulus, Fagussylvatica, Pinusnigra and Pinussylvestris. Higher up, plant communities of Fagussylvatica dominate, followed by those of Pinussylvestris with some Abiesalba and Piceaabies. The mire is formed in a depression and covers an area of 6 ha, fed by precipitation and surface runoff. During spring the water depth can increase to 50 cm due to rapid snow melt. The mire is surrounded by an almost pure forest of Pinussylvestris with an admixture of Piceaabies, Abiesalba, Fagussylvatica, Betulapendula, Sorbusaucuparia, Quercusdalechampii and an undergrowth of Juniperuscommunis, Vacciniummyrtillus, Vacciniumvitis-idaea (Fig. 68). The mire vegetation is represented by sparse moss cover of Sphagnumangustifolium, Sphagnumplatyphyllum, Sphagnumsubsecundum and herbs like Carexriparia, Carexnigra, Carexacuta, Carexechinata, Eriophorumangustifolium, Galiumpalustris, Juncuseffusus, Juncusconglomeratus, Potentillaerecta, Potentillapalustris, Ranunculusrepens, etc. During the last decades most of the mire hummocks were overgrown by pine trees (Bozilova et al., 1989; Huttu nen et al., 1992; Tonkov et al., 2013, 2014).
1A2E40A1-3FE6-5142-85ED-7F439846A0E3
A view of Mire Kupena (Photo: R. Bradshaw).
https://binary.pensoft.net/fig/1672933
<italic>Coring, lithology, radiocarbon dating and chronostratigraphical considerations</italic>
Three sediment cores different in length were obtained in 1984, 1986 and 2009 with the help of Dachnowsky hand-coring equipment and Russian peat sampler. The Cores Kupena-1 (1984) and Kupena-2 (1986) were collected from the central part of the mire, about 50 m apart. The Core Kupena-3 (2009) was collected from the peripheral northeastern part. The corings in 1986 and 2009 were very difficult because of the extremely hard sediments (silty gyttja/sandy clay) of the deepest parts. The lithology of the cores is the following: Core Kupena-1 (0-40 cm peat, 40-110 cm gyttja, 110-125 cm clay gyttja, 125-130 cm sand, 130-170 clay gyttja) (Bozilova et al., 1989); Core Kupena-2 (0-85 cm peat, 85-135 cm peaty gyttja, 135-150 cm silty gyttja) (Huttunen et al., 1992; Bozilova et al., 2011) and Core Kupena-3 (0-56 cm peat, 56-60 cm dark clay, 60-70 cm peat, 70-90 cm grey detritus gyttja clay, 90-110 cm grey sandy clay, 110-130 cm gray detritus gyttja clay, 130–200 cm sandy grey clay) (Tonkov et al., 2013, 2014). The radiocarbon age of 15 sediment samples from the three cores was determined and the results are shown in Table 18. The two radiocarbon dates LuS-8989 and LuS-9332 from the lower part of Core Kupena-3 confirmed the Middle Pleniglacial age of the sediments studied. The rest of the radiocarbon dates from this core refer to the Lateglacial and the Holocene. An important consideration established from the pollen diagram of this core (Fig. 69) is that most of the Late Pleniglacial is not represented, either due to very low sediment accumulation rates or, more likely, to a hiatus. The lateglacial section is of c. 25 cm thickness unlike the other two cores. In conformity with the radiocarbon measurements and the pollen stratigraphy, the cores Kupena-2 (Fig. 70) and Kupena-1 (Fig. 71) are of similar age and extend back to the Lateglacial (Huttunen et al., 1992). At the beginning of the Holocene the sedimentation rate was c. 0.014 cm/yr, whereas after 8300 cal. yrs. BP it changed to c. 0.004 cm/yr which reflects a former lake basin with a very complex topography (Tonkov et al., 2014). In general, the three cores display a very low sedimentation rate for the last 8000 years when only 40-50 cm of sediment was accumulated. Another important issue is the placement of the Lateglacial/Holocene boundary in the pollen diagrams from cores Kupena-2 (Fig. 70) and Kupena-1 (Fig. 71). The pollen diagram from Core Kupena-3 (Fig. 69) clearly indicates this boundary by the steep decline of Artemisia and Chenopodiaceae pollen curves (level 113 cm) and the rise of the total tree pollen attributed mainly to deciduous tree taxa. In case the evidence from the palynostratigraphy is accepted, then the Lateglacial/Holocene boundary in the pollen diagrams from Core Kupena-2 (Fig. 70) and Core Kupena-1 (Fig. 71) can be defined at 97 cm and 73 cm, respectively, and thus disregarding the radiocarbon ages Ua-1553 and INRNE-100.
Pollen analysis for all cores was performed at 5 cm interval and three percentage pollen diagrams are constructed (Figs 69, 70 and 71). The differences observed in the nomenclature of the plant taxa are due to differences in the experience of the pollen analysts. For each core six specific local pollen assemblage (LPAZs) are recognized. Their brief description is presented starting with the leading role of Core Kupena-3.
Comparison of the palynostratigraphy and chronology for sites in the Western Rhodopes and Rila mountains.
https://binary.pensoft.net/fig/1672940
LPAZ Kup3-1 (200-183 cm, Artemisia-Chenopodiaceae-Pinus) (30000?-28000 cal. yrs. BP)
The total herb pollen dominates with 60-80%, attributed mainly to Artemisia up to 40%, Chenopodiacae up to 15% and Poaceae with 5-15%. Values below 5% are recorded for Achillea-type, Dianthus-type, Scleranthus, Galium-type, Apiaceae, Brassicaceae. The tree pollen is represented by Pinusdiploxylon-type 20-35%, Pinuspeuce 4%, Betula, Quercuscerris-type and Juniperus each with 2-3%. A few pollen grains of Picea, Abies, Corylus, Tilia, Carpinusbetulus, Alnus and even Juglans are also found. Characteristic features are the abundance of microspores of Isoetes 10%, some Cyperaceae pollen and Polypodiaceae spores.
LPAZ Kup3-2 (183-143 cm, Pinus-Artemisia-Chenopodiaceae-Betula) (28000-24000 cal. yrs. BP)
The total tree pollen reaches 60% in this zone. High percentages are recorded for Pinusdiploxylon-type 40%, accompanied by Pinuspeuce 5-8%, Betula and Quercusrobur-type each with 2-4%. Pollen grains of Picea, Abies, Juniperus, Corylus, Fagus are frequent in all samples. Pollen of Ephedradistachya-type is established for the first time. Substantial changes in the representation of the herb pollen taxa are not visible, with the exception of some decline for Artemisia to 20-30%. The microspores of Isoetes reach maximal values of 20%. Pollen of Typha/Sparganium-type and Potamogeton is also determined.
LPAZ Kup3-3 (143-113 cm, Artemisia-Chenopodiaceae-Pinus) (15000?-11600 cal. yrs. BP)
At the bottom of this zone the tree pollen curve reaches its lowest values of 5-10% and then increases to 30-55% at the top of the zone. Pollen of Pinusdiploxylon-type is c. 8-10%, Pinuspeuce 5%, Betula, Juniperus and Quercusrobur-type each with c. 5-7%. Pollen of Carpinusbetulus and Carpinusorientalis/Ostrya is found with rather low percentages. The dominant pollen types are Artemisia 40-50% and Chenopodiaceae with a peak of 32%, while Poaceae shows constant values below 10%. The variety of herb pollen is represented also by Caltha-type 10%, Ranunculus-type 5%, Brassicaceae 5%, Dianthus-type 3%, Achillea-type, etc. Pollen of Cyperaceae, Polypodiaceae, Potamogeton, Typha/Sparganium-type and spores of Polypodiaceae are recorded. The presence of Isoetes microspores becomes sporadical.
LPAZ Kup3-4 (113-78 cm, Pinus-Betula-Quercetum mixtum-Fagus) (11600-9200 cal. yrs. BP)
The total tree pollen curve reaches 65-80%, contributed by Pinusdiploxylon-type 20-25%, Betula, Quercusrobur-type and Quercuscerris-type each with c. 5%. Peaks of 7% are recorded for Abies and Fagus. Pollen of other deciduous trees like Ulmus, Corylus, Tilia, Carpinus is also present. In this zone is determined pollen of Fraxinusexcelsior-type, Humulus/Cannabis-type and Vitis. The herb pollen taxa are represented by Poaceae up to 10%, Artemisia 15-10%, Chenopodiaceae, Achillea-type, Ranunculus-type, Rumex, Plantagocoronopus-type, Brassicaceae, Apiaceae, etc. The presence of pollen of Cyperaceae is up to 20%.
LPAZ Kup3-5 (78-33 cm, Quercetum mixtum-Pinus) (9200-4000 cal. yrs. BP)
This zone contains the highest proportion of deciduous tree pollen, with the main contributions by Quercusrobur-type 10%, Ulmus 6%, Betula 6% and Tilia 3%. There is a reduction in the presence of Abies and Fagus. Pollen of Pinusdiploxylon-type and Pinuspeuce reaches 30% and 10%, respectively. Among the herb pollen taxa an increase for Poaceae up to 15% is established, together with Ranunculus-type 15%, Brassicaceae 7%, Apiaceae, Achillea-type, traces of Triticum-type, etc. The local elements are represented by Cyperaceae with 30-40%, Typha/Sparganium-type up to 10%, Potamogeton up to 20% and trilete fern spores. The last finds of Isoetes microspores are recorded.
LPAZ Kup3-6 (33-0 cm, Pinus-Fagus-Abies) (4000 cal. yrs. BP-until recent)
Pollen of tree taxa is attributed mainly to Pinusdiploxylon-type up to 55% in the uppermost samples, Pinuspeuce 12%, Fagus 15-20% and Abies 12%. Picea pollen increases to 3% and Carpinusorientalis/Ostrya-type reaches 5%. Deciduous trees like Quercus, Ulmus and Tilia decline. Compared to the previous zone, the participation of herb pollen is quite similar represented by Poaceae 10%, Plantagocoronopus-type 3%, Rosaceae, Brassicaceae, etc. Pollen of Chenopodiaceae nearly disappears while Artemisia is sporadically found. A continuous presence of Triticum-type pollen is recorded. The local elements are represented by Cyperaceae, trilete fern spores and low proportions for Polypodiaceae, Typha/Sparganium-type and Potamogeton.
Core Kupena-2 (Figs 70 and 72)
LPAZ Kup2-1 (150-117 cm, Poaceae-Pinus-Artemisia) (14000-12800 cal. yrs. BP)
The total tree pollen curve starts with very low values and reaches 52% but then declines to 12.8% at the transition to the next zone. The most important tree taxa are Pinusdiploxylon-type up to 34.7%, Juniperus 7%, Betula 5% and Pinuspeuce 4.5%. The remaining tree taxa such as Corylus, Quercusrobur-type, Quercuscerris-type, Tilia, Ulmus, Carpinusbetulus, Carpinusorientalis/Ostrya, Fraxinusexcelsior and Ephedradistachya-type have values below 1%. The characteristic herb pollen taxa are Poaceae up to 60%, Artemisia 10% and Chenopodiaceae below 5%. The rest of the herbs are present each with c. 1%. Spores of Equisetum reach 14%. Pollen of Cyperaceae dominates, accompanied by Potamogeton 20%, spores of Sphagnum up to 20%, Typha/Sparganium-type 5%. Traces of Isoetes microspores are established.
LPAZ Kup2-2 (117-97 cm, Artemisia-Poaceae-Chenopodiaceae) (12800-11600 cal. yrs. BP)
Pollen of herb taxa dominates in this zone with 85%, attributed to Poaceae 40-60%, Artemisia 35%, Chenopodiaceae 10-15%. The pollen curve of Pinusdiploxylon-type shows low values c. 4-5% and Betula is below 5%. The other coniferous and deciduous trees/shrubs are present with minimal percentages. The find of Ephedradistachya-type pollen is worth to be mentioned. This zone marks the maximal participation of Cyperaceae pollen and spores of Equisetum up to 30%.
LPAZ Kup2-3 (97-67 cm, Betula-Quercetum mixtum-Poaceae) (11600-8200 cal. yrs. BP)
The total tree pollen curve rises from 25% to 75%. The regular occurrence of Quercusrobur-type up to 35%, Quercuscerris-type 10%, Ulmus 8%, Tilia 3% and Fraxinusexcelsior starts in this zone, accompanied by Betula 10%. Single pollen grains of Fagus, Abies, Picea, Cornus, Humulus/Cannabis-type, Vitis are determined. The pollen curve of Poaceae declines to 15% at the transition to the next zone, while Artemisia and Chenopodiaceae are present with minimal values. Pollen of Brassicaceae, Rumex, Ranunculaceae and Linum slightly increases.
LPAZ Kup2-4 (67-27 cm, Quercetum mixtum-Corylus) (8200-5300 cal.yrs. BP)
The total tree pollen curve keeps the same values to the uppermost part of the diagram. At the beginning of this zone the continuous pollen curve of Corylusappears and reaches 10% There is a rise for Carpinusbetulus pollen up to 3%. The main occurrence of thermophilous plants such as Euonymus and Hedera is in this zone. No changes are recorded for the participation of the herb taxa. The final record of Isoetes microspores is registered.
LPAZ Kup2-5 (27-12 cm, Abies-Picea-Pinus) (5300-2000 cal. yrs. BP)
In this zone the pollen curves of Abies and Picea reach maximal values of 22.5% and 7.5%, respectively. At the transition to the next zone the pollen curve of Fagus starts a gradual rise, while Tilia, Ulmus, Carpinusbetulus and Fraxinusexcelsior decrease to c. 1%. A slight rise of Triticum-type pollen is recorded.
LPAZ Kup2-6 (12-0 cm, Pinus-Fagus-Poaceae) (2000 cal. yrs. BP-until recent)
This pollen zone is characterized by the quick rise of Pinusdiploxylon-type up to 51.5%. The same tendency is observed for Fagus with a maximal value of 18%. The pollen curve of Abies declines to 2-3% and most of the other trees, with the exception of Betula, show very low values. An increase is recorded for Poaceae pollen curve up to 20% and 2-3% for Artemisia. The presence of Triticum-type, Hordeum-type and Plantago lanceolata pollen should be mentioned.
Core Kupena-1 (Fig. 71)
LPAZ Kup1-1 (170-133 cm, Artemisia-Pinusdiploxylon-Poaceae-Juniperus)
The total tree pollen is 20-30%, represented by Pinusdiploxylon-type 10-22%, Juniperus 8-4%, Betula 2-3%. The rest of tree/shrub taxa participate with low values or sporadically (Quercus, Alnus, Salix, Carpinusbetulus, Ephedra, Abies, Fagus, Picea). In this zone the herb pollen dominates, attributed to Artemisia 38-30%, Poaceae 12-18%, Chenopodiaceae 11%, Ranunculaceae 2-3%, Apiaceae, Thalictrum, Caryophyllaceae, Apiaceae, Galium-type. Pollen of water plants such as Myriophyllum, Potamogeton, Lemna, Typha/Sparganium-type is also recorded.
LPAZ Kup1-2 (133-104 cm, Pinusdiploxylon-Poaceae-Artemisia-Betula)
The participation of tree pollen rises to 50%, contributed by Pinusdiploxylon-type up to 44%, Betula 8%, Pinuspeuce 1-2%, Juniperus 1-3% and Quercus 2%. Pollen of Artemisia and Chenopodiaceae declines to 10-12% and 3-5%, respectively. Poaceae registers a local maximum of 22%. Pollen от Geum-type, Plantagomajor/media-type and Cirsium-type appears in the record. The presence of Cyperaceae pollen is 10-20%.
This zone is characterized by low values for the total tree pollen 9-15%, interrupted by two steep maxima of 40% (level 95 cm) and 60% (level 90 cm), attributed mainly to Pinusdiploxylon-type 25-45%, Betula 6-8% and Quercus 2-3%. Pollen of Ephedra (distachya-type and fragilis-type) is also determined. Maximal values are recorded for pollen of Artemisia 40-55%, Poaceae 25%, Chenopodiaceae 15% and Asteraceae 5%. Pollen of water plants is absent with the exception of Lemna 8%. Maximal percentages are established for pollen of Cyperaceae 45-67%.
LPAZ Kup1-4 (73-43 сm, Betula-Quercetum mixtum)
This zone is well defined by the steep rise of the tree pollen curve up to 65-70%, due to Betula 16%, with subsequent maxima for Quercus, Ulmus, Fraxinusexcelsior-type with 40%, 15% and 5%, respectively. The pollen curves of Tilia 2-4%, Carpinusorientalis/Ostrya, Alnus and Corylus appear. The participation of herb pollen taxa is rather low, represented by Poaceae 5-8%, Artemisia 2-3%, Asteraceae, Rumex, Galium-type each with 1-2%. Pollen of Potamogeton and spores of Dryopteris-type are recorded in this zone.
The total tree pollen curve reaches a maximum of 80% (level 35 сm), attributed to Corylus 18%, Quercus 25%, Ulmus 6%, Fraxinusexcelsior-type 5%, Fagus 4%. The pollen curves of Carpinusbetulus, Acer, Abies and Picea start in this zone. Among the herb pollen taxa can be mentioned the appearance of Hordeum-type 3%, Filipendula and the presence of Plantagolanceolata, Plantagomajor/media-type and Cerealia-type.
LPAZ Kup1-6 (13-0 см, Pinusdiploxylon-Fagus)
The curve of Pinusdiploxylon-type rises abruptly at the beginning of the zone to a maximum of 64%, accompanied by Fagus 6%, Carpinusorientalis/Ostrya and some Picea. The pollen curves of Corylus and Quercus steeply decline to 1-3%. Pollen of Juglans, Juniperus and Vitis is determined in all samples. The herb pollen assemblage is characterized by Poaceae 15%, Asteraceae, Cichoriaceae, Ranunculaceae, Galium-type, Hordeum-type, Plantagolanceolata and Plantagomajor/media-type. Pollen of Cyperaceae, Lemna and Typha/Sparganium-type is present with low values.
Peat bog Beliya Kanton (site 22)
This peat bog is located in the coniferous belt of the central part of the Western Rhodopes Mountain at 1547 m (41°44’05.16”N, 24°08’23.17”E) near the road to Dospat town, southwest from the artificial reservoir Shiroka Polyana (Fig. 3). It was formed in a depression and has almost a rectangular shape, about 380 m long and 250 m wide, crossed by a meandering stream. The peat bog is bordered by Pinussylvestris-Piceaabies forest and Sphagnum sp., Nardusstricta, Agrostiscapillaris, Eriophorumangustifolium, Deschampsiacespitosa, Carex sp. grow on the bog surface (Bozilova et al., 2000; Lazarova et al., 2011; Marinova et al., 2023) (Fig. 73).
C172D9C2-4E65-53A6-A54C-71C40C3EB3A5
A view of Peat bog Beliya Kanton (Photo: D. Ivanov).
https://binary.pensoft.net/fig/1672941
<italic>Coring, lithology, radiocarbon dating and chronostratigraphical considerations</italic>
Two cores were collected from this site. The first one BK-1 is 70 cm long and was collected with Dachnowsky hand-coring equipment while the second one BK-2C is 105 cm long and was collected with a Russian corer from the central part of the peat bog. The lithology of the cores is the following: Core BK-1 (0–63 cm peat, 63–70 cm sand) (Bozilova et al., 2000), Core BK-2C (0-47 cm slightly decomposed Cyperaceae peat, 47-52 cm gyttja, 52-57 cm grey-yellow clay, 57-78 cm gyttja, 78-105 cm grey sandy clay) (Marinova et al., 2023). The radiocarbon age of 5 samples (macrofossils, charcoal and peat) was determined and the results are shown in Table 19. The radiocarbon ages and the lithology of Core BK-2C provide valuable information on the complicated sedimentation process and the following points need attention:
Radiocarbon dates from Peat bog Beliya Kanton.
Lab. code
Depth (cm)
14C age (BP)
14C age cal. BP, ±2σ (mid-point)
Material dated
Core BK-2C
LuS-8983
21-23.5
405±50
530-310 (420)
Carexrostrata fruits
LuS-8984
42.5-45
1445±50
1520-1280 (1400)
Carexrostrata fruits
LuS-8985
57.5-60
7015±60
7960-7710 (7835)
charcoal
LuS-8986
65-67.5
8020±60
9030-8640 (8835)
charcoal
Core BK-1
KL-3415
45-65
6300±70
7420-7010 (7215)
peat
The interval 78-105 cm of grey sandy clay deposited lacks radiocarbon control but the pollen stratigraphy, when compared with radiocarbon dated sites from the same area, indicates Early Holocene age.
The change in the lithology from grey sandy clay to gyttja at level 78 cm has occurred c. 10 000 cal. yrs. BP, in case the deposition time based on the two radiocarbon dates LuS-8985 and LuS-8986 is accepted.
After c. 7900 cal. yrs. BP a significant change in the local hydrological regime of the site has occurred, manifested by the deposition of grey-yellow clay. Part of the sediment was probably eroded by the stream thus causing a hiatus which duration is difficult to estimate. One hypothesis might be that this hiatus probably covered several centuries or a thousand years. After the stream changed its course again the sedimentation eventually re-established very slowly with gyttja overlain by quickly accumulated sedge peat.
The correlation of both cores is a bit problematic, partly due to the single radiocarbon date for Core BK-1, but is possible by considering the behaviour of the pollen curves of the main tree taxa.
<italic>Pollen analysis</italic>
Pollen analysis of both cores was performed at 5 cm interval and two percentage pollen diagrams are constructed (Core BK-2C, Fig. 74; Core BK-1, Fig. 75). The values in brackets refer to Core BK-1. Four local pollen assemblage zones (LPAZs) are recognized (BK-1 to BK-4) and brief description is as follows:
9C21EBD4-E015-5DD7-BBBB-83B365C2C79E
Percentage pollen diagram of Peat bog Beliya Kanton BK-2C.
Percentage pollen diagram of Peat bog Beliya Kanton BK-1.
https://binary.pensoft.net/fig/1672943
LPAZ BK-1 Core BK-2C (105-77 cm, Pinusdiploxylon-Betula-Poaceae-NAP)
Pollen of herb taxa prevails in a couple of samples, represented by Poaceae 10-20%, Achillea-type 10-12%, Cichoriaceae up to 12%, Brassicaceae 7%, etc. The tree pollen is attributed mainly to Pinusdiploxylon-type 30-58%, Betula and Quercus each with 5%. The participation of Juniperus, Picea, Abies, Ephedra (distachya-type and fragilis-type), Tilia, Ulmus, Corylus, Juglans is below 5% each or sporadical. A peak of trilеte fern spores (40% at level 85 cm) is recorded. The aquatic plants are represented by Potamogeton and Typha/Sparganium-type.
The total tree pollen curve rises and reaches 80% (95%), contributed by Pinusdiploxylon-type 40-60%, Quercus 11%, Corylus 8%, Ulmus 4.7%, Betula 3.7% (25%), Fagus 2%, Tilia 2.3%. Single pollen grains are determined from Abies, Picea, Ephedra (distachya-type and fragilis-type), Salix, Carpinusorientalis/Ostrya, Juglans. The herb pollen taxa are represented by Poaceae up to 15% (37%) and low frequencies for Artemisia, Achillea-type, Ranunculaceae, Rosaceae, Galium-type, Rumex. The participation of Cyperaceae pollen is 55% (30%) and for the trilete fern spores is below 10%.
Pollen of Pinusdiploxylon-type is 30-50%, followed by Picea up to 13%, Fagus 6.8% (2%), Betula up to 7%, Alnus 8.2%, Carpinusorientalis/Ostrya 4%, Abies 2% (12%), etc. The herb pollen taxa are represented by Poaceae 4-8% (50%) and a number of them with low percentage values. In this zone pollen of Cyperaceae displays a maximum of 48-52%.
Pollen of Pinusdiploxylon-type dominates with 55-60%. The pollen curve of Picea declines to 4% followed by a rise to 13% in the uppermost sample. A similar tendency is observed for the pollen curve of Fagus after a maximum of 9% (12%). The pollen percentages of other tree taxa are Quercus up to 10%, Carpinusorientalis/Ostrya, Betula, Abies and Corylus each below 5%. Pollen of Juglans is regularly found. No significant changes in the presence of the herb pollen taxa are recorded compared to the previous zone.
<italic>Plant macrofossil and charcoal analyses</italic>
The core BK-2C was also sampled for macrofossil analysis in 5 cm thick slices. The sample volume ranging from 34-41 cm3 was estimated by volumetric displacement. For quantification of the main peat components, 3 cm3 subsamples were taken and all of the recognisable plant fragments, for example Sphagnum leaves, were counted. After soaking in water all 15 samples were sieved through meshes of 1, 0.5 and 0.25 mm holes. The macrofossils were sorted and identified under stereomicroscope with magnification up to 56×. Charcoal particles were placed into two classes: > 2 mm and < 2 mm, i. e. identifiable and not identifiable wood. The charred wood fragments from the first group were determined under reflecting light microscope. The results of the analysis are plotted on a plant macrofossil diagram (Fig. 76). The plant macrofossils (needles, seeds, nutlets, fruits, coniferous wood, charcoal particles) are quantified as absolute numbers per sample volume of 40 ml, while the main peat components such as fragments of leaf epidermis, roots and leaves of mosses as absolute numbers per sample volume of 3 ml (Marinova et al., 2023). Five local macrofossil assemblage zones (LMAZs) are recognized (BKm-1 to BKm-5) and their content is briefly presented:
82027C2E-A2A8-5A2F-80D9-2DC6AA521CB2
Plant macrofossil diagram of Peat bog Beliya Kanton BK-2C.
https://binary.pensoft.net/fig/1672944
LMAZ BKm-1 (90-78 cm)
The macrofossil record is poor and comprises only few finds of Vaccinium sp. seeds, Eriophorum sp. fruits and Sphagnum leaves.
LMAZ BKm-2 (78-57 cm)
Seeds of Vaccinium sp., fruits of Eriophorum sp. and Juncus sp., nutlets of Carexcf.rostrata, Carex sp. and Sphagnum leaves are present. Fragments of charred coniferous wood and charcoal particles of various sizes are abundant in the upper part of the zone (8800-7800 cal. yrs. BP). The macrofossil record finishes in compact, dried layer (level 58-62 cm) with relatively high concentration of macrocharcoal (smaller than 2 mm and bigger than 0.25 mm). The origin of charred material is mainly from non-arboreal vegetation. Few traces of Sphagnum leaves are found but charred stems of mosses are numerous.
LMAZ BKm-3 (57-50 cm)
This zone corresponds to a hiatus. Nutlets of Carexcf.rostrata, Carex sp., fruits of Juncus sp., Sphagnum leaves and charcoal particles are found in the single sample analysed. A fragment of Pinus sp. needle is also determined.
LMAZ BKm-4 (50-26 cm)
A large number of Carexcf.rostrata and Carex sp. nutlets, Eriophorum sp. and Juncus sp. fruits are identified, alongside with fragments of leaf epidermis, roots and stems of various sedges, Sphagnum leaves and charcoal particles.
LMAZ BKm-5 (26-4 cm)
The presence of conifers around the site is confirmed by needles of Pinus sp., Piceaabies, Abiesalba, male cones of Piceaabies and fragments of charred coniferous wood. Seeds and fruits of various herbs such as Potentilla sp., Luzula sp., Poaceae, Carexcurta, Carex sp., Juncus sp. and vegetative remains of mosses are identified. Charcoal particles are also present.
Lake Blatisto (site 23)
This lake at 1540 m (41°37’17.26”N, 24°40’41.27”E) belongs to the group of the Smolyan Lakes. They are situated in the coniferous belt of the eastern part of the Western Rhodopes Mountain on several swampy terraces along a small river in an area with a pyroclastic rocktype dating from the Oligocene and consisting of rhyolite (Fig. 3). The lakes were formed after landslides originating from failure of the southern slope of the surrounding mountain ridge, probably after an earthquake. This lake is the second highest situated lake of the group being 178 m long and 158 m wide, with an area of c. 1.7 ha and a maximum water depth of 4 m. Its bottom is sandy with boulders and gravel (Ivanov, 1964). The northern and western slopes are covered by a dense Piceaabies forest with some admixture of Abiesalba, Pinussylvestris and Juniperuscommunis. Remarkable are the enormous, still growing Sphagnum islands which occupy nearly 60% of the lake surface (Fig. 77). Between the islands and the borders of the lake the vegetation consists of Carexacuta, Carexechinata, Carexrostrata, Juncuseffusus, Eleocharispalustris, Equisetumhiemale, Equisetum fluviatile, Menthaaquatica, Hypericumtetrapterum, Menyanthestrifoliata, etc. The surrounding meadows are dominated by grasses and scattered stands of Pinussylvestris, Betulapendula and Juniperuscommunis. The present-day vegetation composition in the area of the lakes has been influenced by grazing of domestic animals, cultivation of cereals and potatoes, timber production, and more recently, the construction of tourist complexes and hotels (van Hu is et al., 2013, 2013a).
08E495A5-0697-50CB-80B1-A0AEC2DA1289
A view of Lake Blatisto (Photo: E. Komitov).
https://binary.pensoft.net/fig/1672945
<italic>Coring, lithology and radiocarbon dating</italic>
The sediment core is 460 cm long and was collected with a Streif corer in sections of one meter from an island covered by Sphagnum in the central part of the lake. The lithology of the sediments is: 0-150 cm Sphagnum-Equisetum peat, 150-300 cm peat with plant remains, 300-370 cm sedge peat, 370-400 cm peat with sand and 400-460 cm sandy gyttja. The radiocarbon age of 2 bulk sediment samples was determined and the results are shown in Table 20. The nearly 5-meter core spans a rather short period of time starting from the first centuries AD until present. The sediment accumulation rate has been very quick particularly after the development of Sphagnum started. By extrapolation the age of the bottom sandy gyttja can be provisionally assigned to c. 400 AD or a bit older.
Radiocarbon dates from Lake Blatisto.
Lab. code
Depth (cm)
14C age (BP)
14C age cal. BP, ±2σ (mid-point)
Cal. AD (mid-point)
Material dated
GrN-8441
208-215
575±55
660-510 (585)
1290-1440 (1365)
peat
GrN-8442
420-428
1530±60
1540-1310 (1425)
410-640 (525)
gyttja
<italic>Pollen analysis</italic>
The core was sampled every second centimeter. The presence of the most common pollen taxa and spores is presented on a percentage pollen diagram (Fig. 78). The levels where charcoal particles of various sizes were observed are also indicated on the diagram. On the pollen diagram five local pollen assemblage zones (LPAZs) are recognized (B-1 to B-5). Brief descriptions are as follows:
65FC5008-1451-55BA-828E-65DEA48AB76A
Percentage pollen diagram of Lake Blatisto.
https://binary.pensoft.net/fig/1672946
LPAZ B-1 (460-400 cm, Poaceae-Cerealia-Quercus) (~400 AD-590 AD)
This zone is characterized by the highest herb pollen frequencies between 60% and 80%, attributed mainly to Poaceae up to 40%, the cultivars Cerealia-type up to 12% and Secale 5%. The anthropogenic indicators such as Rumex, Plantago, Urtica, Artemisia, Cichoriaceae are recorded with 5-10%. The deciduous trees are represented by Quercus up to 15%, Fagus 5-10%, Betula 5%, Carpinusbetulus, Carpinusorientalis/Ostrya and Corylus each below 5%. The conifers are present with comparatively low values: Pinusdiploxylon-type up to 10-12%, Picea below 5%, Abies and Juniperus with scattered pollen grains. Charcoal is regularly found.
LPAZ B-2 (400-315 cm, Pinusdiploxylon-Picea-Poaceae) (590 AD-910 AD)
The most characteristic feature is the temporal decline of the total herb pollen to 20%-30%, due to Poaceae 10%, the disappearance of the cereals and the reduction of the anthropogenic indicators Rumex, Plantago and Urtica (level 380 cm). The pollen curves of Pinusdiploxylon-type and Picea rise to 35-40% and 20-25%, respectively. The percentages of the deciduous trees keep the same values. A tendency to a rise of Fagus and Abies is recorded at the transition to the next zone. Lower values are established for pollen of Poaceae and Cyperaceae. Charcoal is nearly absent.
LPAZ B-3 (315-200 cm, Fagus-Picea-Poaceae) (910 AD-1360 AD)
The total tree pollen curve fluctuates between 50% and 80%, with maximal values for Fagus 20%, Abies 10%, Quercus 7%, and continuous presence for Carpinusbetulus, Carpinusorientalis/Ostrya, Corylus, Alnus and Betula each below 5%. The pollen curve of Pinusdiploxylon-type declines to 10-20%, while Picea is c. 10-15%. Among the herb pollen taxa should be mentioned Poaceae 15-30%, Brassicaceae, Asteraceae, Cichoriaceae and the secondary anthropogenic indicators Galium-type, Rumex, Plantago and Urtica. Pollen of Triticum-type, Secale and Cerealia-type appears again. The highest percentages for spores of Polypodiaceae and a constant presence of charcoal are recorded.
LPAZ B-4 (200-135 cm, Pinusdiploxylon-Picea-Fagus) (1360 AD-1600 AD)
In this zone the total tree pollen reaches maximal values above 90%, due to Pinusdiploxylon-type up to 60%, Picea 10-18%, Fagus 15%, Betula, Alnus, Carpinusbetulus and Carpinusorientalis/Ostrya each up to 5%. Pollen of Juniperus is scarcely found. The lowest percentages are recorded for Poaceae 5-10% and for most of the herb taxa such as Asteraceae, Cichoriaceae, Rumex, Plantago.
LPAZ B-5 (135-0 cm, Pinusdiploxylon-Picea-NAP) (1600 AD-until present)
The total herb pollen increases to 50-55%, attributed to Poaceae 45%, Cichoriaceae 5%, Rumex, Plantago, Caryophyllaceae, Cerealia-type 10%, with a constant presence of Secale and Triticum-type. The continuous pollen curve of Juniperus reaches a maximum of 20%. Pollen of Pinusdiploxylon-type and Picea is present with up to 50% and 15%, respectvely. Most of the deciduous trees participate with low values. Among the hygrophytes most common are Menyanthes and Equisetum. Spores of Sphagnum are regularly found.
<italic>Plant macrofossil analysis</italic>
Samples of 10 cm3 sediment were taken at 10 cm interval, boiled in 5% KOH and sieved in four fractions through meshes of 0.5, 0.25, 0.16 and 0.1 mm holes. The content of the fractions was examined under a binocular with 10× or 25× magnification. All available seeds and some plant remain (leaves of mosses, small stems, etc.) were separated. The results are plotted as histograms representing the absolute number of determinable seeds per sample volume of 10 cm3 (Fig. 79). On the diagram four local macrofossil assemblage zones (LMAZs) are recognized (Bm-1 to Bm-4) which reveal successive changes in the lake vegetation development and its surroundings. Their content is briefly described:
371549FD-AA2B-5897-84EA-092BCE8F9546
Plant macrofossil diagram of Lake Blatisto.
https://binary.pensoft.net/fig/1672947
LMAZ Bm-1 (460-360 cm) (~400 AD-740 AD)
The highest abundance of seeds is in this zone. Most of them originate from the marshy vegetation and swampy meadows: Juncuseffusus, Juncusarticulatus, Carexechinata, Carexrostrata, Carexcurta, Eleocharispalustris, Menthaaquatica, Montiafontana. Small quantities of seeds were determined from plants growing on drier places such as Poapratensis, Ranunculusrepens, Potentillaerecta, Prunellavulgaris, Hypericum sp. The presence of Saginaprocumbens and Agrostis sp. seeds as indicators for sandy habitats complete the general picture of the local vegetation. Noteworthy is the absence of seeds from trees and shrubs.
LMAZ Bm-2 (360-275 cm) (740 AD-1070 AD)
The presence of seeds from marshy species sharply decreases and there are only scattered finds of Carexechinata, Juncuseffusus, Juncusbufonius and Juncusarticulatus. Seeds of Ranunculusrepens and Agrostis sp. are regularly found and few from Poaceae and Saginaprocumbens.
LMAZ Bm-3 (275-170 cm) (1070 AD-1470 AD)
An increase is recorded for seeds of Carexechinata, Carexcurta, Juncuseffusus and of grasses (Poaceae, Agrostis sp., Poapratensis). Only in this zone are found a nutlet from Fagus and seeds from Betula sp. and Alnusincana.
LMAZ Bm-4 (170-0cm) (1470 AD-until recent)
Seeds are rarely present in this zone which can be explained by their low state of preservation in the Sphagnum-Equisetum peat. Most common are the finds of Carexechinata, Carexcurta and Juncusbufonius. Seeds of Menyanthestrifoliata are determined. Among the plants growing on drier places can be mentioned Prunellavulgaris and Potentillaerecta.
5.3 Vegetation history in the Western Rhodopes MountainMiddle Pleniglacial – Lateglacial
In accordance with the radiocarbon chronology the lower part of Core Kupena-3 spans a time interval from c. 30000 cal. yrs. BP until c. 24000 cal. yrs. BP (pollen zones Kup3-1 and Kup3-2, Figs 69 and 72). This is the first oldest terrestrial palynological record recovered from a montane area in Bulgaria that starts in the Middle Pleniglacial. The reconstruction of the vegetation cover reveals that the mountain slopes were covered by sparse pine forest, most probably composed of Pinussylvestris, Pinusnigra and Pinuspeuce with stands of Betula, and shrubland of Juniperus-Ephedra on dry sandy places among herb communities dominated by Artemisia, Chenopodiaceae, Poaceae, Apiaceae, Achillea, Ranunculus, Dianthus, Galium and other species. At lower altitudes, under more favorable microclimatic and edaphic conditions, groups of deciduous (Quercus, Carpinus, Tilia, Ulmus, Corylus, Alnus, Fagus) and coniferous (Abies, Piceaabies) trees thrived. The regional presence of such a large variety of trees and shrubs confirms that this part of the mountain has served as one of the montane Middle Pleniglacial refugial places on the Balkans. Gradually, the pine forests with groups of Betula and Juniperus started to expand at the expense of the herbs and over the course of several millennia until c. 24000 cal. yrs. BP the tree vegetation constituted an important part of the plant cover. The wider distribution of trees/shrubs in the study area resulted from climate improvement, which can be associated with interstadial conditions. The extended and improved GICC05 Greenland ice core timescale marks the start of several interstadials GI-4, GI-3 and GI-2 at 28900, 27780 and 23340 cal. yrs. BP, respectively ( Blockley et al., 2012). Taking into account dating uncertainties and likely lags in vegetation response there is a potential match between the duration of pollen zone Kup3-2 (c. 28530-24650 cal. yrs. BP) and the above interstadials of Greenland warming. For the first time, therefore, an interstadial episode during the Middle Pleniglacial was palynologically recognized from the Rhodopes Mountain.
By that time the Mire Kupena resembled a shallow lake fed by rainfall and water from snow melt. The local hydrological conditions favored the growth of Isoetes ( Lazarova et al., 2012). The species Isoeteslacustris grows today in some glacial lakes in the Northern Pirin Mountain together with Potamogeton, Typha and Sparganium species.
The lack of palynological information for the time interval 24000-15000 cal. yrs. BP is most probably a reflection of an important transformation in the hydrological regime of the lake. A lowering of the water level, indicated by the sharp decline of Isoetes and the rest of the hydro- and hygrophytes, probably resulted from the dry climate that prevailed during the Late Pleniglacial, including the Last Glacial Maximum. This dry climate would have contributed to extremely low sediment accumulation rates, or more likely, to a hiatus until the beginning of the Lateglacial c. 15000 cal. yrs. BP (Tonkov et al., 2014). Congruently with the Last Glacial Maximum vegetation reconstruction for the Balkans (Jalut et al., 2005), the harsh environmental conditions in the Western Rhodopes Mountain during this period restricted tree vegetation at low and middle elevations to localities that provided sufficient air and soil moisture. Vast areas were dominated by herb vegetation of steppic character composed of Artemisia, Chenopodiaceae, Poaceae and other cold-dry tolerant species.
The Lateglacial is represented in all three cores from Mire Kupena with different in length sections which confirms the complicated sedimentation process. The low time resolution of Core Kupena-3 for this interval (pollen zone Kup3-3, Figs 69 and 72) does not allow to reconstruct in detail the changes in the vegetation cover. Nevertheless, the general picture of the vegetation pattern in the surroundings of the basin revealed that herb communities with various representatives of Artemisia, Chenopodiaceae and Poaceae and a number of cold-resistant heliophilous herbs from Achillea, Cichoriaceae, Dianthus, Galium, etc. dominated in the landscape particularly during the stadial Younger Dryas. The palynological evidence from Cores Kupena-2 and Kupena-1 indicates a local spread of pines (Pinussylvestris, Pinusnigra and Pinuspeuce) with some Betula and Juniperus during a short-term amelioration of the climate which can be associated with the Bølling/Allerød interstadial (pollen zones Kup2-1 and Kup1-2, Figs 70 and 71) At lower elevations stands of more moisture demanding deciduous and coniferous trees existed, such as Quercus, Corylus, Ulmus, Fagus, Carpinus and Abies. The hydro- and hygrophytes also resumed their presence in and around the lake represented by Cyperaceae, Polypodiaceae, trilete ferns, Potamogeton, Myriophyllum and Isoetes.
Another paleoecological record from the Western Rhodopes Mountain, which dates to the onset of the Lateglacial, originates from a peatland at 1400 m (41°45’24.6”N, 24°08’45.6”E) in the coniferous forest belt of the locality Shiroka Polyana. Today, the site is surrounded by forest of Pinussylvestris and Piceaabies with single trees of Pinuspeuce. The age of the lateglacial sediments is confirmed by the single radiocarbon date of 13080±55 14C yrs. BP (15480 cal. yrs. BP) at the bottom part of the sequence with silt deposited. The lateglacial assemblages are dominated by herb pollen, attributed mainly to Poaceae, Artemisia, Chenopodiaceae and other cold-tolerant herbs (Fig. 72). Low frequencies of pollen of trees and shrubs from Pinusdiploxylon-type, Pinuspeuce, Betula, Juniperus, Quercus, Corylus, etc. are continuously recorded. The pollen stratigraphy from this site does not allow to distinguish an interstadial/stadial cycle. This weakness of the lateglacial palynological subdivision at Shiroka Polyana is probably a reflection of the location of the site in the interland of the Western Rhodopes Mountain where the climate changes during the Lateglacial were moderate (Filip ovitch, Lazarova, 2003; Stefanova et al., 2006a; Bozilova et al., 2011).
Holocene
In the Early Holocene tree communities started to dominate the landscape in the area of Mire Kupena, particularly broad-leaved forests of Quercus with Tilia, Ulmus, Fraxinusexcelsior, some Carpinusbetulus, Carpinusorientalis, Ostryacarpinifolia, and later on Corylus (pollen zones Kup3-4, Kup2-3 and Kup1-3, Figs 69, 70 and 71). The temporary increase of Fagus and Abies, and the re-appearance of minor quantities of pollen of Picea, testify that the climate has become milder and moister. On more open areas at higher elevations a slight expansion of pine communities (Pinussylvestris, Pinusnigra and Pinuspeuce) together with stands of Betula and Juniperus took place, which was commensurate with increased soil development and stabilization. The herb vegetation has become more diverse, partly enriched with species from Rosaceae, Brassicaceae, Apiaceae and Ranunculus.
The slopes in the interior parts of the Western Rhodopes Mountain, around the site Beliya Kanton, were covered by pine forest, admixed with Betula, Juniperus, shrubland of Ephedra and undergrowth of ferns among patches of herb communities composed of Poaceae, Cichoriaceae, Achillea, Artemisia, Brassicaceae, Ranunculaceae and Apiaceae species. At lower altitudes were distributed groups of broad-leaved tree vegetation composed of Quercus, Tilia, Ulmus, Carpinusorientalis, Ostryacarpinifolia. In places with sufficient air and soil moisture thrived stands of Fagus, Abies and Piceaabies, while Alnus and Salix were distributed along streams and brooks (pollen zone BK-1, Fig. 74). The scarce macrofossil record provides little information on the local vegetation but, quite probably, the deposition of sandy clay led to the existence of a shallow lake overgrown with sedges in the peripheral parts, while Typha, Sparganium and Potamogeton were spread on open water surface. The development of the forests until 8800 cal. yrs. BP featured an expansion of the broad-leaved tree vegetation dominated by Quercus with Tilia, Ulmus and Corylus which reached its maximal distribution. At higher altitudes pine forests with stands of Abies and Betula, as well as few Piceaabies, enlarged their area mainly at the expense of the herb vegetation. The macrofossil record points that the shallow water basin was gradually transformed into a peat bog overgrown with sedges, mosses and semi-shrubs. Indications of local fires are provided by numerous charcoal fragments, charred stems of Eriophorum sp. and charred coniferous wood (zone BKm-2, Fig. 76).
At Shiroka Polyana locality forests of Pinus expanded between 11000 and 10000 cal. yrs. BP with a maximum extension at c. 10500 cal. yrs. BP. Later on, over the course of several centuries, Betula and Quercus increased and were firmly established after 8800 cal. yrs. BP. The herb vegetation dominated by Poaceae and less Artemisia and Chenopodiaceae species persisted until c. 9000 cal. yrs. BP and low humidity was probably the reason for the continuation of the steppe vegetation into the Early Holocene in the interland of the Western Rhodopes Mountain. Between 8800 and 8300 cal. yrs. BP a slight increase of Abies is recorded and after 7800 years ago the mixed oak forests started to retreat, replaced at many places first by Corylus and subsequently by Abies and Fagus. Around 6200 cal. yrs. BP a short-term expansion of Pinuspeuce was recorded, followed by the final establishment and spread of Piceaabies, some Abiesalba and later by Fagus and Carpinusbetulus. The last tree immigrant in the Western Rhodopes Mountain was Piceaabies, which tree began to invade areas particularly in the interior parts, when the shaping of a coniferous belt has started (Stefanova et al., 2006a; Bozilova et al., 2011).
In the area of Mire Kupena from 8300 cal. yrs. BP onwards until 4700 cal. yrs. BP the composition of the forests remained nearly the same, except for some reduction of Fagus, Carpinusorientalis, Ostryacarpinifolia and Corylus. The share of Tilia and Ulmus in the oak communities slightly increased (pollen zone Kup3-4, Fig. 69) and these forests reached their maximal distribution. A short-term enlargement of the pine forests is also observed. Sedge dominated peat began to form at the edges of the lake indicative of overgrowing and lowering of the water level. This change in the hydrological regime caused the disappearance of Isoetes and the spread of marshy communities.
Important changes in the vegetation cover are recorded after 4700 cal. yrs. BP. The dynamic processes of tree migrations during the Late Holocene completed with the establishment of the recent vegetation pattern. First of all, Fagus started to gain importance and to some extent Abies and Piceaabies, chiefly at the expense of the mixed oak forests. On drier places Carpinusorientalis and Ostryacarpinifolia became important elements. Secondly, the coniferous forests dominated by Pinussylvestris with some Pinuspeuce, Pinusnigra and Abies started quickly to occupy the vicinity around the Mire Kupena. In these forests the admixtures of deciduous trees were preferably distributed on south-facing slopes. The start of Pinus expansion was precisely radiocarbon dated at 2070 cal. yrs. BP (pollen zone Kup2-6, Fig. 70). In many places fragmented mixed coniferous-deciduous communities developed, attributed not only to climate change but also to human interference in the natural forest cover. The first convincing signs of human presence are documented by the continuous presence of Triticum-type pollen since c. 4700 cal. yrs. BP (pollen zone Kup2-5, Fig. 70).
In the Late Holocene the paleoecological records display important changes in the tree vegetation. The contemporary coniferous belt in the Western Rhodopes Mountain dominated by Pinus was established and communities of Piceaabies and Fagus, mixed with Pinus and Abies on some places, spread in the region. In general, the broad-leaved tree vegetation declined, particularly its components Tilia and Ulmus, and was restricted to its present-day distribution range. Some enlargement of Carpinusbetulus, Carpinusorientalis and Ostryacarpinifolia is observed as well of Alnus on wetter places. The proportion of the herb vegetation around Peat bog Beliya Kanton continued to decrease although its diversity was enriched with various species of Ranunculaceae, Rosaceae, Apiaceae, Brassicaceae, etc. The peat bog began intensively to be overgrown by sedges and mosses while water plants such as Potamogeton were preserved in isolated places with deeper water.
During the last centuries the general trend in the vegetation development around Peat bog Beliya Kanton comprised a further enlargement of Pinus-Piceaabies forests, alongside with a wider distribution of Fagus and Carpinusbetulus predominantly on north-facing slopes. The abundance of needles of Pinus sp., Piceaabies, Abies and male cones of Piceaabies confirms the spread of the coniferous woods (zone BKm-5, Fig. 76). The diverse herb communities were composed of Poaceae, Ranunculaceae, Brassicaceae, Caryophyllaceae and Asteraceae species and the bog vegetation was dominated by various Carex and moss species. The human presence and activities are confirmed by the presence of Juniperus, Juglans, Rumex, Cirsium-type, Galium (pollen zone BK-4, Fig. 74) and by Plantagolanceolata and Hordeum-type (pollen zone BK-4, Fig. 75). The fragments of charred wood testify to tree felling and fire clearances on flat ground in order to obtain pastures for cattle-breeding.
In the vicinity of Shiroka Polyana the vegetation development in the Late Holocene was characterized by the vast distribution of Pinus forests, partially replacing Piceaabies, and resulting in the establishment of the contemporary coniferous belt composed of Pinus, Piceaabies and mixed pine-spruce communities, with rare admixture of Abies and Pinuspeuce. Signs of lasting anthropogenic presence at altitudes of 1400-1500 m were registered by the sharp rising participation of Artemisia, Chenopodiaceae, Rumex, Urtica and Plantago (Filipovitch, Lazarova, 2003).
Detailed information on the vegetation history and human impact for the last 2000 years can be traced from the paleoecological record of Lake Blatisto, Smolyan area (van Huis et al., 2013, 2013a). In the first centuries AD the area around the lakes was intensively used for agricultural activities, cattle- and stock-breeding (pollen zone B-1, Fig. 78). The local inhabitants cultivated Secale and other cereals as shown by the presence of pollen of Cerealia-type (Avena, Hordeum-type). The find of Artemisia, Chenopodiaceae and Brassicaceae pollen can be considered as indicative for waste fields and leads to the conclusion that shifting cultivation was presumably practiced in the vicinity of the lake. The relatively low percentages of Pinus pollen (most probably Pinussylvestris) and Picea, compared to those of deciduous trees, shows that forest clearances by tree felling and, possibly, fires took place on a large scale in the coniferous belt close to the lake around 500 AD, while beech and oak forests with some Tilia and Ulmus at lower altitudes remained less disturbed. During this old cultural phase grazing was common indicated by the frequent occurrence of ruderals and grassland species including Rumex, Urtica, Plantago, Cichoriaceae and Caryophyllaceae. The regular presence of Juglans pollen confirms its cultivation.
The open water of the lake was surrounded by marshy vegetation composed of species from Cyperaceae, Juncaceae, Typhaceae, Alisma, Equisetum, etc. Swampy grasslands and drier pastures were presumably located close to the lake while the arable fields were situated at some distance, and this can explain the absence of seeds from cultivars in the deposits in spite of their abundance as pollen.
The period between 590 AD and 910 AD was marked by a rapid regeneration of the coniferous forests composed of Pinus, Piceaabies and some Abies after the period of human activity (pollen zone B-2, Fig. 78). The fields in the highlands were more or less abandoned probably after exhaustion of the soil on the terraces by intensive cultivation in the preceding period. The distribution of the deciduous trees was restricted to lower altitudes or in more remote locations. The stands of Betula could be considered as an intermediate stage between the clearances during the preceding period and the development of the coniferous and deciduous forests. The continuous presence of meadow plants pointed to the existence of grasslands frequently used for grazing.
The natural forest regeneration until 1360 AD continued with an increasing importance of the deciduous elements. Beech in particular, expanded on the mountain slopes pushing spruce to higher altitudes. The favorable climatic conditions around X-th cent. AD, i.e. increased air-humidity and milder temperatures (Cowie, 2007), have had possibly a positive influence on the development of the deciduous trees. Meanwhile, Abies also enlarged its areas forming monodominant or mixed communities with beech or spruce.
The terraces were still used for grazing and covered with meadow flora (Rumex, Cichoriaceae, Galium, Plantago, Caryophyllaceae, etc.). The cultivation of cereals seems unlikely or practiced on a very small scale. Quite probably, part of the local population moved to higher situated montane places. Human interference has become more intensified at the end of this period when forest clearings and fires periodically took place to extend meadow land. On more open places in the forests and along the forest edges the pioneers Corylus, Carpinusorientalis, Juniperus, Pinus and to less degree Betula can establish themselves.
After the short second cultural phase forest regeneration started again and the pioneers established on more open places (pollen zone B-4, Fig. 78). The populations of coniferous trees expanded regionally, particularly those of Pinus, reaching maximal distribution in the study area. The conifers formed also mixed stands with beech. The low presence of herbs gives indication that the fields on the terraces were abandoned by the local people and an undisturbed forest development took place.
The presence of seeds from different Carex species and Juncusbufonius, as well as spores from Sphagnum and Equisetum, suggest that the marshy vegetation developed in the shallow parts along the shores of the lake (Fig. 79).
The last stage in the vegetation development which started c. 1600 AD (pollen zone B-5, Fig. 78) was characterized by several alternating regression phases in the forest development caused probably by tree felling, fires and grazing. The individual pollen curves reflect the sequence of these phases: cultivation/grazing-fallow land with pioneers and heliophytes-forest regeneration. However, the rate of forest regeneration was under the influence of the human impact. The enhancement of human activities is demonstrated by the cultivation of Secale, Triticum and other cereals (probably Hordeum), and by the extension of the pasture land and arable fields. Stock-breeding was practiced on a large scale as traced by pollen of Juniperus, ruderals and species from grasslands (Rumex, Cichoriaceae, Plantago, Caryophyllaceae, Asteraceae), and by seeds from Poaceae, Prunellavulgaris, Ranunculusrepens and Apiaceae. In general, over the last centuries the contemporary situation in the study area with the prevalance of forests of Piceaabies, and some Pinussylvestris was established. The decline of deciduous trees (Fagus, Quercus, Carpinus) indicates an impediment of the forest development at lower elevations under the human pressure.
In conclusion, the vegetation history of the Western Rhodopes Mountain displays some common features with the results from the Rila and Pirin mountains. This is best expressed particularly for the Lateglacial when herb “mountain-steppe” vegetation composed of Artemisia, Poaceae species with stands of Pinus, Betula and shrubland of Juniperus-Ephedra dominated the landscape above 1000-1200 m. A number of thermophilous deciduous and coniferous trees (Quercus, Carpinusbetulus, Corylus, Fagus, Abies, Picea) survived the last glaciation in local refugia where the microclimatic conditions were favorable for their growth. The afforestation in the Early Holocene started with broad-leaved forests composed of Quercus with Carpinusbetulus, Carpinusorientalis, Ostryacarpinifolia, Ulmus, Tilia, Corylus and minor amounts of Pinus, Betula and Abies. The formation of a coniferous belt with Pinus, Abies and Piceaabies began around 6000-5500 years ago In the Late Holocene after 4700 cal. yrs. BP Fagus started to gain importance chiefly at the expense of the mixed oak forests, while after 2000 cal. yrs. BP forests of Pinus with some Piceaabies quickly expanded and the recent vegetation pattern was established (Fig. 72). Reliable evidence about human interference in the natural vegetation cover (deforestation, stock-breeding and agriculture) is available from the pollen diagrams and confirmed by the macrofossil finds (charred seeds, wood, twigs, needles) collected from prehistorical settlements and karst caves.
6. VITOSHA MOUNTAIN6.1 Physico-geographical characteristcs and modern vegetation
Vitosha Mountain (peak Cherni Vrah, 2290 m) is one of the highest massifs in Bulgaria located between 42°24’–42°40’N and 20°40’–21°12’E in northwest-southeast direction in the outskirts of the capital Sofia (Fig. 2). The mountain has a dome shape (23 × 17 km) with an area of 268.8 km2 surrounded by three valleys. The mountain slopes descend steeply but there are no deeply incised valleys to divide it into separate parts. The geomorphological development of the mountain has specific features that give it the character of an independent geomorphological unit. It is built from a syenite pluton in its core which at the beginning of the Tertiary was embedded in a shell of Upper Cretaceous volcanic rocks - andesites, andesitic breccias, diorites and others. Tertiary conglomerates and sandstones are exposed in places in the northern and western periphery, and in the southern and southeastern outskirts there are limestones and dolomites. The mountain was formed during the Tertiary and Quaternary through several vertical uplifts and peripheral subsidence, which, together with denudation processes had formed levels of different ages and floodplain terraces. Their modern reflection is plateau-like alignments that give the mountain a sunken character. During the Pleistocene the mountain was not glaciated but the high parts were under the influence of the periglacial climate. Weathering and denudation processes have caused the formation of stone rivers, stone piles, screes and other gravity forms. Of particular importance for the water regime of the mountain are the plateaus with their peat cover, which retain moisture, and from them originates a large part of the rivers as small streams (Nikolov, Jordanova, 2002; Popov, ed., 2014).
Vitosha Mountain is sutuated in the Temperate Continental climate region. The most characteristic features of this climate are the warm summers and cold winters, a large annual air temperature amplitude, a spring maximum and a winter minimum of precipitation. The continental climate above 1000 m changes to montane with mean annual temperatures of 7°C and 3.3°C at 1300 m and 1800 m, respectively. The mean annual precipitation varies from 690 mm at 800 m to 1000 mm at 1700 m and the snow cover usually lasts for five to seven months depending on the altitude (Velev, 2002; Stoyanov, 2014).
The combination of geological, geomorphological, climatic and hydrological conditions determines the diversity of soil and plant cover. Three main soil belts can be recognized. The belt of cinnamon soils stretches out to about 800 m, above it is the belt of brown mountain-forest soils (800-1800 m). The belt of mountain-meadow soils (loamy and peaty) is found above 1800 m. A wide distribution of shallow soils (rankers, lithosols), swampy and peaty soils is also characteristic (Hubenov, 1990; Ninov, 2002).
According to the last geobotanical zoning Vitosha Mountain is a separate region in the Sofia district of the Illyrian (Balkan) Province (Bondev, 2002). The modern vegetation is developed in several altitudinal belts but their boundaries are not distinct and depend on the relief. The slopes from 1100 to 1400 m are covered by mixed oak-hornbeam forests composed of Quercusdalechampii, Quercuscerris and Carpinusbetulus, with admixture of Acerplatanoides, Tiliacordata, Fraxinusexcelsior, Corylusavellana, etc. The average altitude is 1250 m and this belt is to the greatest extent anthropogenically influenced as the modern vegetation is mostly of secondary origin. In the eastern part of the Vitosha Mountain this belt was completely destroyed. Artificial plantations of Pinussylvestris, Pinusnigra, Betulapendula and a large number of ornamental trees and shrubs such as Tilia sp., Quercusrubra, Cornus sp., Ligustrumvulgare, etc. can be seen. Above this belt are distributed forests of Fagussylvatica in the altitudinal zone 1400-1840 m depending on the exposure. Most of these forests are of secondary origin. They are fragmented at many places, monodominant, or mixed at lower altitudes with Carpinusbetulus, Populustremula, Acercampestre, Fraxinusornus, Fraxinusexcelsior, and at higher altitudes with Acerpseudoplatanus, Acerplatanoides, Prunusavium, Abiesalba, Piceaabies. The coniferous belt is represented entirely by the communities of Piceaabies which shape the upper timber-line. The average altitude of this belt is 1870 m, varying from 1700 to 2050 m. The distribution of Piceaabies forests is secondarily fragmented. Two main compact massifs are formed - in the western part between the peaks Chernata skala and Ostritsa and in the eastern part of the mountain where they are included in the Nature Reserve Bistrishko Branishte. In these forests are found few Pinussylvestris, Abiesalba, Sorbusaucuparia, Populustremula and stands of Betulapendula on more open areas. This belt was destroyed in the past in the southern mountain part. Only in the southeastern part today are growing small patches of natural forests of Pinussylvestris. Towards its upper limit the spruce forests become sparser and in their composition are found Juniperussibirica, Vaccinium sp., Alnusviridis, etc. The treeless subalpine zone above 1850 m is occupied by the communities of Juniperussibirica, Nardusstricta, Festucavalida, Festucanigrescens, Festucarubra, Sesleriacomosa, Phleumalpinum, Calamagrostisarundinacea, Anthoxanthumodoratum. The communities of Juniperussibirica are well developed on the steep southern slopes as well as on the entire western part of the subalpine belt. Some of the characteristic accompanying species are Vacciniummyrtillus, Vacciniumvitis-idaea, Vacciniumuliginosum and Bruckenthaliaspiculifolia. In separate places patches of Pinusmugo are observed. They were widespread in the past and subsequently destroyed. The hygrophilous grass and moss communities associated with the flooded areas within this belt are well represented. The most widespread are the formations of Deschampsiacespitosa, Moliniacaerulea, Carexacuta, Sphagnum sp. which are localized on waterlogged soil substrates. Groups of Salixlapponum, Salixwaldsteiniana, Salixcinerea are sporadically distributed on waterlogged terrains. There is no clearly defined alpine belt on the Vitosha Mountain and only in its highest parts the alpine fragmented vegetation is represented by the communities of Sesleriacomosa, Juncustrifidus and Vacciniumuliginosum. The composition of the present-day vegetation has been highly influenced by anthropogenic activities and the timber-line has been artificially lowered (Filipovitch, 1988, 1989; Velchev, 2002; Apostolova, Meshinev, 2002; Alexova, Gyurova, 2012; Tonkov, Possnert, 2016).
6.2 Study sitesPeat bog Kapaklivets-Platoto (site 24)
This peat bog at 1837 m (42°35’20.7”N, 23°17’05.6”E) is located in the treeless subalpine plateau zone on the northern slopes of the mountain (Fig. 3). It occupies an area of 0.5 ha with northeast exposure. The bog vegetation is composed of Sphagnum sp., Carexnigra, Eriophorumlatifolium, Eriophorumvaginatum, Trichophorumcespitosum, Festucarubra, Deschampsiacespitosa, Agrostiscapillaris, Nardusstricta, Succisapratensis, Homogynealpina, Bruckenthaliaspiculifolia, Vacciniummyrtillus, Vacciniumvitis-idaea among groups of Juniperussibirica and Salixlapponum. Single trees of Pinussylvestris are visible in the immediate surroundings. Stands of Pinusmugo are growing at a distance of 500 m to the east, while fragments of Piceaabies forests are found at a distance of 750 m to the east/northeast (Tonkov et al., 2025) (Fig. 80).
E1F1202B-02A0-5205-8558-EC03E6E40969
A view of Peat bog Kapaklivets-Platoto (Photo: D. Gyurova).
https://binary.pensoft.net/fig/1672948
<italic>Coring, lithology and radiocarbon dating</italic>
A sediment core 193 cm long was obtained from the central part of the peat bog with modified Wardenaar corer (0-72 cm) and Dachnowsky corer (70-193 cm). The lithology of the sediments is: 0–10 cm Sphagnum mosses, 10-40 cm slightly decomposed Sphagnum-Cyperaceae peat with plant remains, 40-120 cm dark brown peat with plant remains, 120-190 cm peaty gyttja and 190-193 cm gyttja with sand. The radiocarbon age of 5 bulk sediment samples was determined and the results are shown in Table 21. The age of the core is estimated at 9000 cal. yrs. BP.
Radiocarbon dates from Peat bog Kapaklivets-Platoto.
Lab. code
Depth (cm)
14C age (BP)
14C age cal. yrs BP, ±2σ (mid-point)
Material dated
AWI-14012.1.1
68-69
3427±30
3820-3580 (3700)
peat with plant remains
AWI-14475.1.1
103-104
4910±54
5850-5480 (5670)
peat with plant remains
AWI-14012.1.1
128-129
5520±29
6400-6280 (6340)
peaty gyttja
AWI-14014.1.1
168-169
7317±31
8180-8030 (8105)
peaty gyttja
AWI-13181.1.1
190-191
8017±25
9010-8770 (8890)
peaty gyttja
<italic>Pollen analysis</italic>
Pollen analysis was conducted at 5 cm interval and a percentage pollen diagram is constructed (Fig. 81). Pollen accumulation rates (PAR) for the major tree/shrub and herb taxa are also calculated (Fig. 82). On the pollen diagram six local pollen assemblage zones (LPAZs) can be recognized (Vit-1 to Vit-6) (Figs 81 and 83). Brief descriptions are as follows:
65F78D16-E8AC-55C1-B8E9-1278FC0BEFD3
Percentage pollen diagram of Peat bog Kapaklivets-Platoto.
Pollen accumulation rates (PAR; pollen grains cm-2 yr-1) for the main tree/shrub and herb taxa from Peat bog Kapaklivets-Platoto plotted against age in cal. yrs. BP.
Comparison of the palynostratigraphy and chronology for sites located west of the Struma river.
https://binary.pensoft.net/fig/1672951
LPAZ Vit-1 (193-177 cm, Pinusdiploxylon-Abies-Quercus-Corylus) (9000-8400 cal. yrs. BP)
The total tree pollen dominates with 65-80%, attributed to Pinusdiploxylon-type 30-20%, Quercuscerris-type 10-13%, Corylus 5-10%, and a characteristic maximum of Abies 20% (level 180 cm). The rest of the tree taxa participate each with less than 5%. Single finds of Fagus and Picea pollen are also recorded. The herb pollen is represented mainly by Apiaceae 5-8%, Poaceae 5%, Artemisia up to 5%, Cirsium-type, Brassicaceae, Cichoriaceae, etc. The participation of Cyperaceae pollen and Polypodiaceae spores is rather low. The total PAR of tree taxa varies from 3000 up to 13800 grains cm-2 yr-1, contributed by Pinusdiploxylon-type 1200-4900, Abies up to 3400, Quercuscerris-type 500-1600, Corylus 500-1400, etc. The total PAR of herb taxa is from 1000 up to 3000-3700 as shown by Poaceae 750, Apiaceae 750, Artemisia 550, etc.
LPAZ Vit-2 (177-133 cm, Corylus-Quercus-Betula) (8400-6500 cal. yrs. BP)
This zone is well defined by the dominance of Corylus pollen with 25-30%, accompanied by Betula up to 12% and Quercuscerris-type 10-15%. The participation of other deciduous tree taxa such as Ulmus, Tilia and Quercusrobur-type slightly increases, whilst minor quantities of Carpinusbetulus, Carpinusorientalis/Ostrya and Abies pollen are recorded. Pollen of Juglans and Vitis is regularly found. Among the herb pollen taxa are Apiaceae with up to 15%, Poaceae, Artemisia, Cichoriaceae. The presence of Cyperaceae pollen increases to 10%. The total PAR of tree taxa varies between 2000 and 6200 grains cm-2 yr-1, attributed to a maximum of 2250 for Corylus, accompanied by Betula 1250, Pinusdiploxylon-type and Quercuscerris-type 500-750 each, etc. The total PAR of herb taxa is 2500-3000, due to a maximum of 1250 for Apiaceae, Poaceae 500, Artemisia up to 300, etc.
LPAZ Vit-3 (133-103 cm, Carpinusbetulus-Abies-Corylus-Quercus) (6500-5600 cal. yrs. BP)
Pollen of Carpinusbetulus features a steep maximum of 30% (level 110 cm), accompanied by Abies 5-20%, Corylus 25-10%, Quercuscerris-type up to 20%, Pinusdiploxylon-type 15-30%. Single pollen grains of Fagus and Picea are also determined. There are no important changes in the participation of the herb taxa, except for the decline of Apiaceae pollen. The total PAR of tree taxa rises to 12000 grains cm-2 yr-1 with a maximum of 20000 (level 110 cm), contributed by Pinusdiploxylon-type 3100, Quercuscerris-type 2500-2900, Corylus up to 2500, a steep maximum for Carpinusbetulus 7000 (level 110 cm), Abies 1800, etc. The total PAR of herb taxa is c. 2100-2400, represented by Poaceae up to 1400, Artemisia 450, etc.
LPAZ Vit-4 (103-63 cm, Abies-Carpinusbetulus-Quercus) (5600-3350 cal. yrs. BP)
The total tree pollen dominates with 80-90%. For this zone is characteristic the maximal presence of Abies pollen with 20-35%, Carpinusbetulus 10%, Quercuscerris-type 10-12%, Corylus 10-5%. The pollen curves of Fagus and Picea appear with 2-4%. Among the herb taxa the first record of Plantagolanceolata pollen is established. The total PAR of tree taxa reaches 9000 grains cm-2 yr-1, repesented by Abies up to 3500, Pinusdiploxylon-type up to 2100, Corylus up to 1000, Picea 500, Fagus 200, etc. The total PAR of herb taxa is up to 2500, as shown by Poaceae 510, Cichoriaceae 250, Artemisia 260, etc.
LPAZ Vit-5 (63-43 cm, Picea-Fagus-Pinusdiploxylon-Betula) (3350-2300 cal. yrs. BP)
The total tree pollen dominates with 60-80%, attributed to Picea 15%, Fagus 10%, Betula 5-10%, Pinusdiploxylon-type 25%, Abies 5%, Quercuscerris-type, Corylus. The herb pollen is represented by Poaceae up to 15%, Artemisia, Cichoriaceae, Cirsium-type, Apiaceae. The total PAR of tree taxa reaches 5000 grains cm-2 yr-1, contributed by Pinusdiploxylon-type 1500-1750, Picea up to c. 1000, Betula 750, Fagus 500-700, etc. The total PAR of herb taxa is 2400, attributed to Poaceae 600, Brassicaceae and Cichoriaceae each 220, Artemisia 200.
LPAZ Vit-6 (43-5 cm, Poaceae-Pinusdiploxylon-Fagus-Juniperus) (2300-270 cal. yrs. BP)
The total herb pollen rises to 50%, contributed by Poaceae 30%, Cichoriaceae 5%, Artemisia 6%, Plantagolanceolata 4%, Rumex 3%, etc. Pollen grains of Secale, Triticum-type, Xanthium-type, Filipendula are determined in this zone. An increase for Cyperaceae pollen of 12% is recorded. The uppermost pollen spectra are dominated by Pinusdiploxylon-type 30-40%, Fagus 10-15%, Corylus 10%, Carpinusorientalis/Ostrya 7%, Juniperus 3-5%. Pollen of Juglans is regularly found. The total PAR of tree taxa steeply declines from 2500 to 500-1000 grains cm-2 yr-1, contributed by Pinusdiploxylon-type 350, Fagus up to 120, Picea 100, etc. The total PAR of herb taxa is 500, attributed mainly to Poaceae 250.
Peat bog Konyarnika (site 25)
This peat bog is located at 1789 m (42°35’11.3”N, 23°14’46.7”E) in the treeless central plateau zone (Fig. 3). It occupies an area of c. 0.6 ha and borders to the west a sparse forest of Piceaabies. The bog vegetation is composed of Sphagnum sp., Carexnigra, Carexechinata, Moliniacaerulea, Potentillaerecta, Dactylorhizacordigera, Sanguisorbaofficinalis, Eriophorumvaginatum, Eriophorumangustifolium, Gentianellabulgarica, Juniperussibirica, Bruckenthaliaspiculifolia, Vacciniummyrtillus, Vacciniumvitis-idaea, etc. (Fig. 84).
8657E10F-1F5D-5849-961E-BEB16560D6DA
Coring at Peat bog Konyarnika (Photo: D. Gyurova).
https://binary.pensoft.net/fig/1672952
<italic>Coring, lithology and radiocarbon dating</italic>
A sediment core 80 cm long was obtained from the central part of the peat bog with modified Wardenaar corer. The lithology of the sediments is: 0-23 cm live Sphagnum mosses, 23-50 cm slightly decomposed Sphagnum-Cyperaceae peat and 50-80 cm decomposed peat with plant remains. The radiocarbon age of 5 bulk sediment samples was determined and the results are shown in Table 22. The age of the core is estimated at 2750 cal. yrs. BP. The lowermost 10 cm of peat were deposited very slowly for c. 1400 years while the uppermost 50 cm of slightly decomposed peat and live Sphagnum were accumulated probably during several centuries. The radiocarbon age AWI-14476.1.1 of 36±49* BP needs a critical view because it falls within the interval from modern time to a couple of centuries ago. In this case the best solution is to disregard it (Tonkov et al., 2026).
Radiocarbon dates from Peat bog Konyarnika.
Lab. code
Depth (cm)
14C age (BP)
14C age cal. BP, ±2σ (mid-point)
Cal. (BC/AD)
Material dated
AWI-14476.1.1
39-41
36±49*
270-20 (145)
1680-1930 (1805) AD
slightly decomposed peat
AWI-16309.1.1
50
431±14
540-320 (430)
1410-1630 (1520) AD
decomposed peat
AWI-14477.1.2
59-61
981±51
960-740 (850)
990-1210 (1100) AD
decomposed peat
AWI-16310.1.1
70
1462±15
1370-1310 (1340)
580-640 (610) AD
decomposed peat
AWI-13183.1.2
79-80
2631±22
2770-2730 (2750)
820-780 (800) BC
decomposed peat
<italic>Pollen analysis</italic>
Pollen analysis was conducted at 5 cm interval and a percentage pollen diagram is constructed (Fig. 85). On the pollen diagram four local pollen assemblage zones (LPAZs) can be recognized (Kon-1 to Kon-4). Brief descriptions are as follows:
682DDBCA-779A-5439-AA39-210777825522
Percentage pollen diagram of Peat bog Konyarnika.
https://binary.pensoft.net/fig/1672953
LPAZ Kon-1 (80-67 cm, Picea-Pinusdiploxylon-Abies-Fagus) (2750-950 cal. yrs. BP)
The total tree pollen curve dominates with 85-75%, attributed to Picea up to 35% (level 75 cm), Pinusdiploxylon-type up to 20%, Abies 8-2% and the rise of Fagus pollen curve up to 10%. The rest of tree/shrub taxa are present with values below 5-10%. Among the herb pollen taxa can be mentioned Poaceae, Artemisia, Cichoriaceae, Apiaceae, Brassicaceae, etc.
LPAZ Kon-2 (67-53 cm, Pinusdiploxylon-Picea-Fagus-Poaceae) (950-560 cal. yrs. BP)
The total tree pollen is c. 80%, contributed by Pinusdiploxylon-type up to 35%, Piceac. 10%, an increase of Fagus from 10% to 20% at the transition to the next zone, Abies 1-2%, Quercus, Corylus, Carpinusbetulus, Betula each below 5%. The presence of Poaceae rises to 10%, accompanied by some Artemisia, Cirsium-type, Apiaceae, Chenopodiaceae, etc. The pollen curve of Cyperaceae starts in this zone.
LPAZ Kon-3 (53-27 cm, Fagus-Pinusdiploxylon-Poaceae) (560-150? cal. yrs. BP)
The pollen curve of Fagus displays a maximum of 30% (level 45 cm), accompanied by Pinusdiploxylon-type 20%, the disappearance of Abies pollen curve, a steep decline of Picea, a short-term rise of Juniperus and the establishment of Juglans pollen. The share of total herb pollen increases to 45%, attributed mainly to Poaceae 15%, Artemisia 10%, Chenopodiaceae 5%, etc. In this pollen zone a group of anthropogenic pollen indicators (Plantagolanceolata 5%, Rumex, Centaureacyanus, Triticum-type, Secale) is recorded. A characteristic feature is the presence of Cyperaceae pollen up to 15% and the determination of the first spores of Sphagnum.
LPAZ Kon-4 (27-5 cm, Picea-Pinusdiploxylon-Fagus) (150? cal. yrs. BP-until present)
The total tree pollen curve rises again to c. 90%, due to Pinusdiploxylon-type up to 60% and Picea up to 30%. Pollen of Fagus declines to 10%, whilst a slight rise is established for the pollen curves of Carpinusorientalis/Ostrya, Corylus and Quercuscerris-type. The herb pollen taxa (Poaceae, Artemisia, Rumex, Geum-type, etc.) are present with rather low values. Spores of Sphagnum dominate in the fossil assemblage.
Peat bog Kumata 1 (site 26)
The investigated site is a small peat bog at 1770 m (42°35’25.54”N, 23°15’06.85”E) located in the vicinity of the touristic hut Kumata (Fig. 3). It occupies c. 0.1 ha and is surrounded by Piceaabies forest with undergrowth of Juniperussibirica, Vacciniummyrtillus and Vacciniumuliginosum. The bog surface is overgrown by spots of Sphagnum sp., Carex sp., Eriophorumlatifolium, Deschampsiacespitosa, Moliniacaerulea, Veratrumlobelianum, etc. (Fig. 86).
2A8504A5-9FE9-59D5-ABA6-60E2872FD5E7
A view of Peat bog Kumata 1 (Photo: S. Tonkov).
https://binary.pensoft.net/fig/1672954
<italic>Coring, lithology and radiocarbon dating</italic>
A sediment core 100 cm long was obtained from the central part of the peat bog with Dachnowsky hand-coring equipment. The lithology of the sediments is: 0-40 cm slightly decomposed Sphagnum-Cyperaceae peat with plant remains, 40-80 cm dark brown Cyperaceae peat and 80-100 cm Cyperaceae peat with fine sand. The radiocarbon age of 3 bulk sediment samples was determined and the results are shown in Table 23. The age of the core is estimated at c. 1300 cal. yrs. BP (Tonkov, Possnert, 2016, 2016a).
Radiocarbon dates from Peat bog Kumata 1.
Lab. code
Depth (cm)
14C age (BP)
14C age cal. BP, ±2σ (mid-point)
Cal. AD
Material dated
Ua-51516
41-43
291±31
460-280 (370)
1490-1670 (1580)
peat
Ua-50937
62-64
751±25
730-670 (700)
1220-1280 (1250)
peat
Ua-50938
92-94
1289±30
1290-1170 (1230)
660-780 (720)
peat
<italic>Pollen and microcharcoal analyses</italic>
Pollen analysis was conducted at 5 cm interval and a percentage pollen diagram is constructed (Fig. 87). Pollen accumulation rates (PAR) for the major tree/shrub and herb taxa are also calculated (Fig. 88). The absolute number of michrocharcoal particles counted on pollen slides is also presented on the pollen diagram. They are divided into two classes: type-1, smaller than 50 µm and indicative of distant fires and type-2, larger than 50 µm and indicative of local fires. This proxy is commonly used by paleoecologists to study the occurrence and intensity of past fires and their effects on ecosystems (Tinner, Hu, 2003). On the pollen diagram three local pollen assemblage zones (LPAZs) can be recognized (K1-1 to K1-3). Brief descriptions are as follows:
Pollen accumulation rates (PAR; pollen grains cm-2 yr-1) for the main tree/shrub and herb taxa from Peat bog Kumata 1 plotted against age in cal. yrs. BP.
https://binary.pensoft.net/fig/1672956
LPAZ K1-1 (100-67 cm, Picea-Pinusdiploxylon-Abies-Fagus) (1350-750 cal. yrs. BP)
The most characteristic features are the dominance of total tree pollen (85-75%) with maximal participation of Picea 45% and its subsequent decline to c. 20%, the rise of Fagus pollen curve from 4% to 10-12%. The pollen values of Pinusdiploxylon-type are below 25% and of Abies are c. 5-7%. Pollen of deciduous tree taxa such as Carpinusbetulus, Quercus, Alnus and Corylus is also present each with 3-6%. Single pollen grains of Juglans are found. The herb pollen is represented mainly by Poaceae 10-12%, Artemisia, Cirsium-type, Apiaceae, Brassicaceae, Cichoriaceae, etc. The participation of Cyperaceae pollen and Polypodiaceae spores is rather low. The average total PAR of tree taxa is c. 5000 grains cm-2 yr-1 with a maximum of 10500, contributed by Picea 3500, Pinusdiploxylon-type up to 3000, Fagus 1250, Alnus up to 700, Quercus up to 600, etc. The total PAR of herb taxa is 2000-3000 as shown by Poaceae 1000, Cichoriaceae 300, Apiaceae 200.
LPAZ K1-2 (67-27 cm, Picea-Fagus-Pinusdiploxylon-Poaceae) (750-250 cal. yrs. BP)
Changes in the participation of the coniferous and deciduous tree taxa are not recorded in the lower part (67-45 cm) of the zone. A slight rise for Juniperus pollen is observed. The share of total herb pollen increases to 25-35%, attributed mainly to Poaceae 15-20%, Artemisia, Achillea-type, Cirsium-type, Rumex, Plantagolanceolata, Filipendula, etc. For the first time pollen of Hordeum-type is determined. In the upper part of the zone (45-27 cm) the total tree pollen curve steeply declines to 35%. The pollen frequencies of Picea, Pinusdiploxylon-type and Abies are considerably reduced to 8-10%, 12-15% and 1-3%, respectively. Pollen of deciduous trees from Betula, Alnus, Carpinusbetulus, Quercus and Corylus displays also minimal values. A short-term rise of Juniperus pollen 5% is recorded, followed by a steep peak of Poaceae pollen curve to 50% (level 30 cm). The total PAR of tree taxa is c. 3000-5000 grains cm-2 yr-1. The share of Pinusdiploxylon-type is 1000-1500, Picea 1000-1750, Fagus up to 750, Corylus up to 600, Quercus 550, Abies up to 500, etc. The total PAR of herb taxa reaches 3000 with a maximum of 5000 (level 30 cm), contributed by Poaceae 1500 with a maximum of 4000, Cichoriaceae 200, Brassicaceae 100.
LPAZ K1-3 (27-0 cm, Picea-Pinusdiploxylon-NAP) (250 cal yrs. BP-until present)
The total tree pollen curve rises again to c. 70% followed by a distinct minimum (level 5 cm) where the lowest pollen frequency for Pinusdiploxylon-type 10% is established. The pollen curve of Picea restores its previous stable values of 15-20%. Pollen of Fagus declines to 5%, whilst a slight rise is established for Betula, Alnus, Carpinusbetulus, Carpinusorientalis/Ostrya and Corylus pollen curves. Among the herb pollen taxa, the presence of Poaceae with 15-20%, Cirsium-type up to 10%, Xanthium, Rumex, Plantagolanceolata, Scabiosa can be mentioned. The total PAR of tree taxa is c. 4000 grains cm-2 yr-1 with a maximum of 6500 (level 25 cm). The share of Pinusdiploxylon-type is c. 1000, Picea 1000, Fagus up to 500 with a maximum of 1500 (level 25 cm), Quercus 400, etc. The total PAR of herb taxa is between 3000 and 5000 (level 25 cm), attributed to Poaceae up to 2500, Cichoriaceae 450, Artemisia 200, Rumex 150.
6.3 Vegetation history in the Vitosha Mountain
For the first time the development of the vegetation in the Vitosha Mountain during the major part of the Holocene, i.e. over the last 9000 years, is archived in the pollen spectra of the Peat bog Kapaklivets-Platoto. The changes in the plant cover since historical time are retrieved in more details from the pollen diagrams of the peat bogs Konyarnika and Kumata 1.
The correlation of the numerous pollen diagrams produced from different parts of the mountain before the present study, was performed on the basis of only two radiocarbon dates (Filipovitch, 1988). The succession of several forest phases since 6300 cal. yrs. BP (mixed thermophilous deciduous forests, hornbeam and coniferous forests, beech and coniferous forests, degradation of the forest cover) was proposed but their chronological duration could not be determined. In our investigation the oldest pollen assemblages from the Peat bog Kapaklivets-Platoto reveal that 9000 years ago the slopes of the mountain were covered by mixed deciduous forests composed of various oak species (mostly Quercuscerris), Ulmus, Tilia, and Corylus on open areas. These forests climbed higher than today. Above them were distributed communities of pine (most likely Pinussylvestris and Pinusmugo) with stands of Betula and Abies, single trees of Piceaabies and Fagus, and shrubland of Juniperus. Alder and willows were growing along the mountain brooks. The herb vegetation was composed of Poaceae, Apiaceae, Brassicaceae, Artemisia and Rumex species. The peat bog in its early stage of existence was situated near the timber-line. Between c. 8750 and 8400 cal. yrs. BP a quick spread of Abies, accompanied by some Piceaabies, Carpinusbetulus and Fagus is recorded, which was most probably a result of climate cooling and increase in air humidity, favorable for the growth of the above species (pollen zone Vit-1, Fig. 81). A similar short-term peak of Abies was established at 9300 cal. yrs. BP from the Northwestern and Central Rila Mountain (Tonkov et al., 2008, 2016).
After 8400 cal. yrs. BP Corylus expanded for the next 2000 years together with some enlargement of the mixed oak forests and Betula. Simultaneously, Pinus partly retreated from its areas, while the growth of Abies, Piceaabies and Carpinusbetulus was restricted to separate stands in isolated places with sufficient soil and air humidity. Also, the first records of Juglans and Vitis pollen point to their presence (pollen zone Vit-2, Fig. 81).
An important transformation in the forest cover is observed after 6500 cal. yrs. BP. It was characterized by the quick spread of Abies and this tree has become the main constituent in the coniferous forest belt together with Pinus (most likely Pinussylvestris). Meanwhile, the maximal expansion of Carpinusbetulus communities was reached c. 5800 cal. yrs. BP and the onset of a partial decline for Corylus and the mixed oak forests was recorded (pollen zone Vit-3, Fig. 81). In general, the forests have become denser as confirmed by the highest PARs of the main tree taxa (pollen zone Vit-3, Fig. 82). The dominance of Abies forests was established after c. 5500 cal. yrs. BP and continued until 3370 cal. yrs. BP, when they quickly declined, replaced by the communities of Piceaabies and Fagus. Spruce has gradually begun to occupy areas since c. 4500 cal. yrs. BP, partly at the expense of Carpinusbetulus, while the mixed oak forests retreated to lower altitudes. By that time, the forest vegetation continued to be compact and dense.
The last millennia marked the wide distribution of Piceaabies and Fagus. Both trees started to expand nearly simultaneously after 3700-3500 cal. yrs. BP. Spruce played an important role in the coniferous forest belt, particularly between 3400 and 2300 cal. yrs. BP, with a maximum at c. 2900 cal. yrs. BP (pollen zone Vit-5, Fig. 81). The presence of beech remained relatively stable until nowadays as a separate forest belt was shaped predominantly on the northern slopes. Evidence is collected that vast areas were deforested at mid-high altitudes between 2300 and 1500 cal. yrs. BP for new pasture land and timber. This reconstruction is justified by the extreme low PARs of the tree taxa, the increase of Poaceae, Artemisia, Cichoriaceae, Chenopodiaceae, and the anthropogenic pollen indicators for stock-breeding and grazing such as Plantagolanceolata, Rumex, Juniperus and Xanthium (pollen zone Vit-6, Figs 81 and 82). The find of cereal pollen from Secale and Triticum-type points to crop cultivation in the foothills of the mountain. The Peat bog Kapaklivets-Platoto was already positioned in the treeless zone above the timber-line which was artificially lowered.
In historical time around 1400 years ago (VI-th cent. AD) the surroundings of the peat bogs Kumata 1 and Konyarnika were overgrown by a dense Piceaabies forest, with an admixture of Pinus (probably Pinussylvestris), some Abies and undergrowth of ferns. Stands of Betula occupied more sandy areas while Alnus was growing on wetter places. At lower altitudes on open places were distributed mixed oak forests with Carpinusbetulus and Corylus. The PAR of Picea (c. 3500 grains cm-2 year-1) confirm that spruce was the dominant tree species in the area (pollen zone K1-1, Figs 87 and 88). Despite that similar PAR are recorded for Pinus, it is well-known that pine is an over-producer of pollen and together with Abies it played a subdominant role in the coniferous forests. The presence of Fagus points that its communities started to enlarge after 430 cal. yrs. BP (XVI-th cent. AD) when Piceaabies declined. Direct evidence for human interference is recorded after 430 cal. yrs. BP by the finds of Rumex, Plantagolanceolata, Xanthium, Triticum and Secale pollen (pollen zone Kon-3, Fig. 85). In the near vicinity of Peat bog Kumata 1 beech colonized free terrains after the occurrence of forest fires around 1270-1180 cal. yrs. BP, confirmed by an increase in the concentration of the microcharcoal particles (pollen zone K1-1, Fig. 87).
Between 750 and 450 cal. yrs. BP (1200-1500 AD) the forest surrounding the Peat bog Kumata 1 was partially opened and the share of the herb component, mostly composed of Poaceae, Artemisia, Achillea-type and Cichoriaceae species, has increased. A large-scale disturbance in the coniferous and deciduous forests took place after c. 450 cal. yrs. BP and lasted for a couple of centuries. The areas occupied by Piceaabies and Pinussylvestris were considerably reduced and, subsequently, the free area was colonized by grasses and stands of Juniperus. The steep peak of microcharcoal particles (level 45 cm) unequivocally suggests the occurrence of forest fires, most of them induced by humans, in order to enlarge the existing pasture land and to obtain timber for various purposes (pollen zone K1-2, Fig. 87). Synchronously, the disturbances in the natural forests were accompanied by a rise of the anthropogenic pollen indicators.
The last 300-400 years of vegetation history was a period of the strongest human impact on the natural vegetation. The coniferous forests partly regenerated but remained fragmented at many places. Fir almost completely disappeared from the vegetation cover of the mountain. The communities of Fagus restored for a short period of time but, subsequently, they were also considerably reduced. Most of the deciduous trees at lower altitudes partly enlarged (Carpinusbetulus, Carpinusorientalis, Quercus) while the increase of Corylus indicated openings of the forest canopy. The constant presence of herb taxa such as Xanthium-type, Cirsium-type, Plantagolanceolata, Rumex confirms that the anthropogenic interventions have taken place in all vegetation belts (pollen zone K1-3, Fig. 87). Following the historical sources, the southern mountain slopes were completely deforested to supply timber to the local population for various purposes including also metallurgy of iron ore and some precious metals (Cholakov, 2025). Mining, metallurgy and cattle-breeding led to extensive deforestation and fires with large degradation of the natural habitats. Also, by that time, the communities of Pinusmugo on the highest mountain slopes were almost completely destroyed (Filipovitch, 1989). In more recent time the creation of tourist paths and infrastructure continues to affect the landscape, though strict protection measures were introduced in certain areas.
7. KONYAVSKA MOUNTAIN7.1 Physico-geographical characteristics and modern vegetation
Konyavska Mountain (peak Viden, 1487 m) is located in the northеrn part of Southwestern Bulgaria, in an area representing a complex mosaic of mountains and small valleys with various directions of extension, with the prevailing being northwest-southeast (Fig. 2). As a morphostructural unit the mountain is separated between the Radomir Basin from the northeast, the gorges of the Struma river from the north and northwest. To the south, the mountain runs to the Kyustendil Basin and to the east and northeast ends to the Bobovdol Paleogene Basin. Geologically and geotectonically, the mountain is well investigated and generally refers to the Transitional block fractured geomorphological area. The deeply cut valleys of the Uglyarska, Blateshnitsa, Konyavska and Klisurska rivers divide the mountain orographically into four parts: Viden (1487 m), Risha (1443 m), Kolosh (1314 m) and Korilovski (991 m). The total area of the mountain is 237 km2 with an average altitude of 929 m. The age of the lithological base ranges from Paleozoic metamorphic rocks to Neogene sedimentary complexes. Several lithological formations have had a decisive influence on the modern morphological appearance, namely, the Triassic carbonate complex, the Late Jurassic complex, the Late Eocene conglomerate-breccia and conglomerates (Bonchev et al., 1960).
During the Tertiary some of the deep valleys became lake basins which were gradually filled with deposits from the surrounding mountains. As a central negative form within the mountain stands the Tschokljovo structural depression which is now occupied by a marshy peatland. It covers an area of 1.8 km2 at an average altitude of 870 m. In general, the main relief of the Konyavska Mountain was formed at the beginning of the Quaternary (Konstantinov, 1979).
The mountain falls on the border between the Temperate Continental climate and the Transitional Continental climate (Dimitrov, 1974). The average maximal temperature for the warmest month is 28°C and for the coldest is -6°C. The average annual precipitation is between 500 and 750 mm, with a minimum in February and a maximum in June (Stanev et al., 1991).
The soils are mainly cinnamomic-forest (chromic Cambisols) and humus-carbonate rich (rendzic Leptosols) (Ninov, 1997). The soil erosion is highly developed where the main rocks are discovered in places there are screes, tunnels and collapses.
According to the last geobotanical zoning Konyavska Mountain is included as a separate region in the Sofia District of the Illyrian (Balkan) Province (Bondev, 2002). The modified mediterranean climate along the Struma river gorge and the interaction between different climatic influences have left their mark on the nature, composition and distribution of the vegetation. The general characteristics of the vegetation cover of the mountain and the adjacent calcareous areas are presented in several publications and floristic reports (Stojanov, 1935, 1941; Bondev, 1991, etc.)
On the western and southwestern slopes of the Risha part where the mediterranean influence along the Struma gorge penetrates the basic plant communities are those of Quercuscerris, Quercuspubescens and Carpinusorientalis. In their composition are found also some transitional-mediterranean elements such as Jasminumfruticans, Juniperusoxycedrus, Paliurusspina-christi, Coronillaemerus, etc. Shrub and herb xerothermic formations are distributed on limestone deforested areas. In the rest of the Risha and Korilovski parts the communities of Quercuscerris are widespread, including Quercuspubescens, Quercusdalechampii, Carpinusbetulus, Acerplatanoides, Acerpseudoplatanus, Corylusavellana, Ostryacarpinifolia. The mixed oak forests occupy large areas along the northern and derived slopes of the Kolosh and Viden parts. The communities of Fagussylvatica are quite common above 1000-1200 m. The natural vegetation of the mountain is strongly disturbed by the anthropogenic impact which resulted in large scale deforestation, the replacement of the natural plant communities by secondary in origin. Partial measures were taken to afforest some areas with Pinussylvestris and Pinusnigra.
7.2 Study siteTschokljovo Marsh (site 27)
This water basin is located in the middle of the Konyavska Mountain at 870 m (42°23’56.08”N, 22°49’31.17”E) (Fig. 3). After drainage in the 1950s until the mid 1980s peat was extracted on a large scale for different purposes. A detailed description of the aquatic vegetation, its floristic composition, formations and associations prior to the beginning of the drainage is presented in several publications (Jordanov, 1929, 1931, 1947). The vegetation of the marsh resembled a specific combination of the lowland fens, swampy shrubs and reed swamps. From the first vegetation type were distributed Heleocharispauciflora, Juncusarticulatus, Triglochinpalustris, Menyanthestrifoliata, Potentillapalustris, etc. Characteristic elements for the vegetation of the swampy shrubs were Salixpentandra, Salixcinerea, Salixrosmarinifolia along with Thelypterispalustris, Sparganiumerectum, Lathyruspalustris, Peucedanumpalustris, Carexacuta, Calamagrostisepigeios, Thalictrumflavum, etc. The reed-swamp vegetation was distributed in the central and partly in the northern and southern parts of the marsh represented by Typhalatifolia, Phragmitesaustralis, Alismaplantago-aquatica, Irispseudacorus, Menthaaquatica, etc. The extensive exploitation of the peat deposits resulted in the destruction of the local vegetation from which only separate fragments were preserved. The marsh was flooded again in the 1980s when the drainage channels were removed and the extraction of peat was stopped. It was declared a protected area in 1992 on a territory of 320 ha in order to preserve the habitats of rare and endangered birds and the peatland itself (Fig. 89).
CD731610-FC66-5F2B-BEF7-9D9A3D794264
A view of Tschokljovo Marsh (Photo: D. Kozuharov).
https://binary.pensoft.net/fig/1672957
<italic>Coring, lithology and radiocarbon dating</italic>
Two cores were collected with Dachnowsky hand-corer equipment from undisturbed peat layers in the southwestern part of the marsh. Core-1 is 445 cm long and the lithology of the sediments is: 0-90 cm marl with peat, 90-300 cm peat with plant remains, 300-350 cm peaty gyttja, 350-400 cm clay with gyttja, 400-405 cm peat, 405-445 cm clay. Core-2 is 240 cm long and the sediment is peat (Tonkov, 1988). The radiocarbon age of 9 samples of bulk sediment was determined and the results are shown in Table 24. They indicate that the age of Core-1 is c. 9000 cal. yrs. BP and of Core-2 c. 3600 cal. yrs. BP (Tonkov, Bozilova, 1992).
Radiocarbon dates from Tschokljovo Marsh.
Lab. code
Depth (cm)
14C age (BP)
14C age cal. BP, ±2σ (mid-point)
Material dated
Core-1
Lu-2169
90-105
1250±50
1290-1060 (1175)
peat
Lu-1991
230-240
2380±50
2700-2320 (2510)
peat
Lu-1990A
274-279
3130±50
3450-3210 (3330)
peat
Lu-2168
353-358
4760±80
5650-5310 (5480)
clay with gyttja
Lu-1989
400-405
6300±65
7420-7020 (7220)
peat
Lu-2167
437-442
8000±110
9250-8580 (8915)
clay
Core-2
LuS-1994A
72-80
1860±50
1930-1630 (1780)
peat
LuS-1993
140-144
2380±50
2700-2320 (2510)
peat
LuS-1992
149-152
2430±50
2710-2350 (2530)
peat
<italic>Pollen analysis</italic>
Pollen analysis was conducted at 5-10 cm interval and two percentage pollen diagrams are constructed (Core-1, Fig. 90 and Core-2, Fig. 91). The uppermost 70 cm of Core-1 contain no pollen. Both pollen diagrams are synchronized and five local pollen assemblage zones (LPAZs) are recognized (TM-1 to TM-5) (Fig. 83). Brief descriptions are as follows:
LPAZ TM-1 (445-400 cm, Quercus-Corylus-Pinusdiploxylon-Abies) (~9000-6200 cal. yrs. BP)
High pollen values are established for Corylus 28% and Quercus 26%. At the transition to the next zone Pinusdiploxylon-type and Abies reach 43% and 28%, respectively. Pollen of Tilia 8%, Ulmus 4% and Carpinusbetulus is also found. The herb pollen taxa are represented by Poaceae 6-8%, Ranunculaceae 2-3%, Rosacae, Achillea-type. The local component includes pollen of Typhalatifolia 45% and Nuphar, spores of Polypodiaceae 150% and Thelypterispalustris.
LPAZ TM-2 (400-300 cm, Abies-Pinusdiploxylon) (6200-3600 cal. yrs. BP)
Pollen of Abies reaches maximal values of 52-54%, accompanied by Pinusdiploxylon-type 20-50%, Quercus 15%, Tilia, Corylus, Betula and Carpinusbetulus. Pollen of Poaceae attains a peak of 50% and the variety of herb pollen taxa is considerable. The pollen curve of Cyperaceae is present with up to 40%.
LPAZ TM-3 (300-235 cm, Pinusdiploxylon-Fagus-Abies) (3600-2400 cal. yrs. BP)
The pollen curve of Fagusappears and rises to 26%. Other deciduous tree taxa such as Quercus 22%, Carpinusbetulus 8%, Corylus 5%, Alnus are also present. Pollen of Abies declines to 19%, while Pinusdiploxylon-type rises up to 50%. The herb pollen taxa are represented by Poaceae 25-8%, Ranunculaceae, Brassicaceae, Apiaceae, etc. Spores of Polypodiaceae reach 28%, together with a sharp increase for spores of Thelypterispalustris with 30% at the transition to the next zone. Hydrophytes and hygrophytes such as Nuphar, Cyperaceae and Typhalatifolia are also present.
LPAZ TM-4 (235-145 cm, Pinusdiploxylon-Abies-Quercus) (2400-1600 cal. yrs. BP)
Pollen of Pinusdiploxylon-type reaches 70-80%. Pollen of Abies fluctuates between 13% and 23%, while Quercus and Fagus are present with 14% and 4%, respectively. Pollen of Cerealia-type and Polygonumaviculare-type is also determined.
LPAZ TM-5 (145-70 cm, Quercus-Fagus-Pinusdiploxylon) (1600-1000 cal. yrs. BP)
The pollen curves of Quercus and Fagus rise to 27% and 17%, respectively. Pollen of Abies declines to 3-4%, while Pinusdiploxylon-type exceeds 80%. The herb pollen taxa are represented by Poaceae 10-15%, Rumex 4%, Ranunculus-type 3%, Cichoriaceae, Cerealia-type, etc. Spores of Polypodiaceae and pollen of Cyperaceae are also recorded.
Core-2
LPAZ TM-3 (240-170 cm, Pinusdiploxylon-Fagus-Abies) (3600-2400 cal. yrs. BP)
Tree pollen dominates represented by Pinusdiploxylon-type 24-60%, Abies 6-18%, Fagus 13%, Quercus 10%, Carpinusbetulus, Corylus. The variety of herb pollen taxa is high, represented by Poaceae, Ranunculus-type, Apiaceae, Filipendula, Rumex, etc. The pollen curves of Cyperaceae and Typhalatifolia rise to 33% and 9%, respectively, accompanied by spores of Polypodiaceae up to 50% and spores of Thelypterispalustris 37%.
LPAZ TM-4 (170-80 cm, Pinusdiploxylon-Abies-Quercus) (2400-1600 cal. yrs. BP)
Pollen of Pinusdiploxylon-type displays a maximum of 60% and then declines to 20%. Pollen of Abies reaches 10-20%, Quercus 20-25%, Ulmus 7% and Salix 4%. A great number of herb pollen taxa are determined, among them Poaceae, Chenopodiaceae, Ranunculaceae, Artemisia, Filipendula, etc. High values for Polypodiaceae spores 32% and pollen of Cyperaceae up to 40% are characteristic, together with pollen from hygrophytes and hydrophytes.
LPAZ TM-5 (80-0 cm, Quercus-Fagus-Pinusdiploxylon) (1600 cal. yrs. BP-until present)
The pollen curves of Quercus 30% and Fagus 11% increase, together with Corylus 5%, Carpinus, Salix, Alnus, etc. Pollen of Poaceae 18%, Plantagolanceolata 5%, Cerealia-type, Polygonumaviculare-type, Secale and Triticum-type is registered. The local component is represented by Typhalatifolia 12%, Cyperaceae 5-6%, spores of Polypodiaceae and Cystopteris, etc.
<italic>Plant macrofossil analysis</italic>
The material for analysis was sampled from Core-1 at 10 cm interval parallel to the samples for pollen analysis. Altogether 40 samples, each of 20 cm3, were processed following a standard procedure with subsequent sieving through meshes with 0.25, 0.5, 1, 2 and 4 mm holes. The macrofossil diagram is constructed on the basis of the absolute number of fruits and seeds found, while the presence of other plant remains (fragments of stems and roots, sporangia, pieces of wood) is indicated with dots (Chakalova et al., 1990) (Fig. 92). Four local macrofossil assemblage zones (LMAZs) are recognized (mTM-1 to mTM-4) and their brief descriptions are as follows:
Plant macrofossils are almost absent. Single fragments of roots and epidermis are found. Pieces of Abies and Betula wood are determined at levels 415 cm and 330 cm, respectively.
LMAZ mTM-2 (295-260 cm) (3800-3000 cal. yrs. BP)
Fruits of Batrachium gr., single finds of Potamogeton sp., Carexrostrata, Polygonum sp., fragments of roots and epidermis are determined.
LMAZ mTM-3 (260-145 cm) (3000-1700 cal. yrs. BP)
This zone is the richest in plant macrofosssils. Fruits of various Carex and Scirpus species dominate which is an indication of marshy area in the periphery of the basin. Fruits and seeds from various herb species such as Potentillapalustris, Menyanthestrifoliata, Lycopus, etc. are determined. The share of Sphagnum and Bryopsida moss remains, and Equisetum stems increases.
The samples are rich in fragments from woody and herb plants. Single finds of fruits from Carexrostrata, Carex gr. and Typha sp. are recorded, together with seeds from Symphytum sp., Polygonum sp. and Chenopodium sp. In the uppermost 50 cm plant macrofossils are absent.
7.3 Vegetation history in the Konyavska Mountain
The palynological and plant macrofossil data provide possibilities for the reconstruction of the vegetation cover over the last 9000 years in one of the lower calcareous mountains in Southwestern Bulgaria. The oldest pollen spectra (pollen zone TM-1, Fig. 90) indicate that the mountain slopes were covered by mixed oak forests and on many open places Corylus appeared as a pioneering element. In the composition of these forests other trees participated such as Tilia, Ulmus, Carpinusbetulus, Carpinusorientalis and Ostryacarpinifolia. Stands of Pinus and Abies, mixed in some places with Betula, were also growing as proved by the find of subfossil wood fragments of Abies and Betula (zone mTM-1, Fig. 92). On the basis of the pollen morphology is not possible to distinguish which pine species prevailed, i.e. Pinusnigra or Pinussylvestris (Bozilova, 1963). It is supposed that on calcareous terrains and at lower elevations black pine was predominantly distributed.
This forest composition existed for nearly 1800-2000 years when the conifers gradually started to enlarge their area replacing the deciduous forests in many places. The main reason for this change was probably an increase in air and soil humidity and c. 6400 cal. yrs. BP Abies started to gain a dominant role. Despite that single pollen grains of Fagus were found in the sediments, beech finally established in this mountain 2000 years later. The scarce data on the herb vegetation suggests that it was composed mainly of Poaceae, Ranunculaceae, Rosaceae, Artemisia species.
The next period in the vegetation development is characterized by the dominance of Abies forests for 3000 years. Fir formed monodominant communities and reached downslope near to the shores of the marsh. The participation of Pinus, bearing in mind its over-representation in the pollen rain, was restricted, and in some places mixed Abies-Pinus communities existed. The oak forests retained their distribution and Tilia was abundant in them. An interesting feature is the continuous presence of Juglans pollen which presumes most likely its native distribution, rather than cultivation by the local people (pollen zone TM-2, Fig. 90).
The subsequent change in the vegetation cover is associated with the spread of Fagus and this process was initiated after 3500 cal. yrs. BP. Beech invaded into the coniferous belt and the first maximum in its distribution was recorded c. 3000 cal. yrs. BP. A characteristic feature was also the most significant presence of Carpinusbetulus, Carpinusorientalis, Ostryacarpinifolia, and a slight enlargement of Corylus on more sunny open places. The herb communities were enriched with species from Poaceae, Rosaceae, Fabaceae, Cichoriaceae, Achillea, etc. Most of them thrived also in the marshy vegetation and in the peripheral drier parts.
The information about the vegetation development in the course of the last 2500 years can be traced in more details from both pollen diagrams (pollen zones TM-4 and TM-5, Figs 90 and 91). The changes in vegetation were caused not only by natural factors but also by the increasing human activity. This assumption is confirmed by the regular finds of anthropogenic pollen indicators such as Cerealia-type, Triticum-type, Secale, Rumex, Plantagolanceolata, Centaureacyanus and Polygonumaviculare-type. The extensive exploitation of the forests resulted in their wide-scale destruction. The area around the marsh is rich in archaeological monuments from Thracian and Roman times such as remains from buildings, water-pipes, ceramics, etc. (Dechev, 1933).
The final enlargement of the beech and oak forests, and partly of hornbeam and hazel, is recorded after c. 1700 cal. yrs. BP. The composition of the pollen assemblages reflects an intensive deforestation which has affected both the deciduous and coniferous forests. Since that time the present-day appearance of the vegetation cover in the Konyavska Mountain was shaped influenced to a considerable extent by the anthropogenic activities.
The results from pollen analysis, determination of plant macrofossils and sediment description (Tonkov, 1988) provide plentiful information about the hydrological regime of the marsh, its origin and the transformations of the local vegetation.
Between 9000 and 5500 cal. yrs. BP the sediment type reflects the existence of a lake with a relatively high-water level. The material deposited is grey clay with traces of lake gyttja. The most common hygrophyte was Typhalatifolia which has overgrown the shores of the lake and c. 7000 cal. yrs. BP the first spores of Thelypterispalustris, one of the characteristic species of the flora for this water basin, were established.
The sedimentation of peaty gyttja, overlain by sedge peat, started since 5500 cal. yrs. BP and served as an indication for a lowering of the water level and the establishment of optimal conditions for the spread of water and marshy plants. This situation is justified by the continuous pollen curve of Cyperaceae and the find of Nymphaea, Nuphar, Typhalatifolia and Alisma pollen. Fruits from typical hydrophytes such as Batrachium gr. and Potamogeton sp. prevail in the sediment record.
The lowland peat bog vegetation type was widely distributed between 2800 and 1700 cal. yrs. BP, represented by Carex, Filipendula and Potentilla species. A typical feature was the local maximum of Thelypterispalustrisc. 2400 cal. yrs. BP and this fern spread in the reed communities (pollen zone TM-4, Fig. 90). The distribution of this vegetation type is archived in the rich macrofossil record represented by fruits of Carex gr., Scirpus gr., Juncus sp., Carexrostrata, Potentillapalustris, fragments of Equisetum stems, and moss remains (zone mTM-3, Fig. 92). As the peat layer became more stable the peripheral parts of the marsh were overgrown by willows and alders.
The sediments accumulated after 1700 cal. yrs. BP appear heterogeneous in composition, ranging from almost pure undecomposed reed peat to fen-carr peat mixed with mineral particles. Sedge communities composed of various Carex, Scirpus, Juncus and Heleocharis species were widely distributed. Fruits of Carex gr., Carexrostrata and Typha sp. are sporadically found, and also seeds/fruits from plants with wider ecological requirements such as Polygonum sp., Symphytum sp., Chenopodium sp., etc. The presence of Alisma, Lythrum and Potamogeton pollen, spores of Sphagnum and Polypodiaceae indicate that 1000 years ago the main vegetation types were already present in the marsh.
8. OSOGOVO MOUNTAIN8.1 Physico-geographical characteristics and modern vegetation
Osogovo Mountain (peak Ruen, 2251 m) is the highest border massif of the Osogovo-Belasitsa mountain range which is situated in Southwestern Bulgaria and in the Republic of North Macedonia (Fig. 2). The northern and northeastern slopes on Bulgarian territory are going down steep to the periphery of Kamenishka and Kyustendil valleys, and to the south the saddle Black Rock is the linkage to the Vlahina Mountain. The massif is composed mainly of Paleozoic metamorphic and intrusive rocks. On the surface in the middle of the mountain reveals a core of the southern Bulgarian granite. Sandstones (Triassic, Tertiary and others) are widespread in the eastern parts. From a geomorphological point of view five denudation levels were formed during the Neogene and the transition to the Quaternary. Small valley glaciers existed in the highest parts of the mountain during the Quaternary glaciations stretching down to c. 1700 m (Velchev, 1995).
The present day climate below 1000 m is Moderate Continental and above this altitude it changes to typically montane. The mean annual precipitation is 700-900 mm with two precipitation maxima in May and November, and a precipitation minimum in August-September. The average annual duration of the stable snow cover is 135 days (Velev, 2002).
The basic soils are cinnamomic-forest (chromic Cambisols), above them are found brown-forest (Cambisols), and the ridge is occupied by montane-meadow (Umbrisols) (Ninov, 1997).
According to the last geobotanical zoning, Osogovo Mountain is included as a separate region in the Western Bulgarian Border Mountain District of the Illyrian (Balkan) Province (Bondev, 2002). The mountain is usually viewed together with the other western border mountains (Vlahina, Maleshevska and Ograzhden) but its vegetation differs in many aspects because of the more northern location and higher altitude. Comprehensive information on the modern vegetation of the Osogovo Mountain can be found in the Vegetation Map of Bulgaria (Bondev, 1991) and in the review of Velchev, Tonkov (1986). Following these basic literature sources the vegetation comprises several altitudinal belts.
The oak forest belt up to 1000 m on the southeastern slopes is dominated by Quercuspubescens, Quercuscerris and Quercusdalechampii with some Carpinusorientalis, Ostryacarpinifolia and Juniperusoxycedrus. Plant communities of Pinusnigra and Fagussylvatica are also found. The beech belt (1000-1900 m) is the most well-developed vegetation belt, composed mainly of monodominant communities of Fagussylvatica. At some areas in the beech belt patches of Abiesalba and Pinusnigra are present. Beech forms the upper timber-line between 1500 and 1900 m. Today a compact coniferous vegetation belt does not exist. Stands or isolated trees of Pinussylvestris grow close, or just above, the timber-line. Remnants of mixed coniferous communities composed of Piceaabies and Abiesalba, highly restricted in distribution, are preserved in the northern part of the mountain between 1100 and 1600 m. The treeless area in the subalpine belt, above the beech forests, is occupied by plant communities of Juniperussibirica, Vacciniummyrtillus, Bruckenthaliaspiculifolia, Chamaecytisusabsinthioides, Nardusstricta, etc. In all vegetation belts, the oak and beech forest belts in particular, the negative consequences of the long-lasting human impact, including deforestation with subsequent erosion and ore-mining activities, are easily visible (Tonkov, 2003a; Lazarova et al., 2015).
8.2 Study sites
In the treeless, mostly flat central part of the mountain, between 1600 and 1800 m just above the beech forests, small peat bogs occur in depressions formed as a result of denudation processes (Velchev et al., 1994). The thickness of the peat layers and the underlying sediments rarely exceeds 1 m. Three peat bogs located nearby springs were selected for study (Fig. 3).
Peat bog Osogovo 1 (site 28)
This peat bog is situated at 1720 m and occupies a small area of c. 50 m2 on a northeastern slope. Stands of Pinussylvestris and Juniperuscommunis grow nearby and patches of Piceaabies were planted (Tonkov, 2003a).
<italic>Coring, lithology and radiocarbon dating</italic>
The core 170 cm long was collected with Dachnowsky hand-corer equipment. The sediment is composed of Cyperaceae peat. The radiocarbon age of 3 bulk sediment samples was determined and the results are shown in Table 25. The estimates from the radiocarbon dating indicate that the age of the core is c. 5000 cal. yrs. BP.
Radiocarbon dates from peat bogs in the Osogovo Mountain.
Lab. code
Depth (cm)
14C age (BP)
14C age cal. BP, ±2σ (mid-point)
Material dated
Osogovo 1
Lu-3420
45-55
790±60
800-640 (720)
peat
Lu-3421
82-98
2220±70
2350-2040 (2200)
peat
Lu-3422
120-130
3350±70
3730-3440 (3580)
peat
Osogovo 2
Hv-12550
65-80
995±75
1060-740 (900)
peat
Begbunar
LuS-6714
20-25
245±70
490-11 (250)
4 mg charcoal
LuS-6713
70-74
3190±50
3560-3330 (3450)
5 mg charcoal
LuS-6712
84-89
3755±60
4360-3920 (4140)
6 mg Carex fruits
<italic>Pollen analysis</italic>
Pollen analysis was performed at 10 cm interval and a percentage pollen diagram is constructed. On the pollen diagram three local pollen assemblage zones (LPAZs) are delimited (OS-1 to OS-3) (Fig. 93). Two of them (OS-2 and OS-3) are also recognized in the pollen diagram from Peat bog Osogovo 2. Brief descriptions are as follows:
9A6CC89E-3192-5935-8D46-755B04DB66CE
Percentage pollen diagram of Peat bog Osogovo 1.
https://binary.pensoft.net/fig/1672963
LPAZ OS-1 (170-95 cm, Pinusdiploxylon-Abies) (~5000-3100 cal. yrs. BP)
Pollen of Pinusdiploxylon-type dominates with 65-45%, accompanied by Abies with 8-10%. Other tree taxa such as Juniperus, Alnus, Quercus, Tilia, Corylus and Carpinus participate each with 2-4%. The herb component is represented by Poaceae with 5% and a number of taxa such as Cichoriaceae, Achillea-type, Cirsium-type, Dianthus-type, Lychnis-type, etc. A characteristic feature is the high values of Scleranthus pollen up to 15-20%.
LPAZ OS-2 (95-55 cm, Pinusdiploxylon-Fagus-Abies) (3100-970 cal. yrs. BP)
The dominance of Pinusdiploxylon-type continues with 45-50%. A local maximum of Abies pollen 12% is followed by a decline to 3-4%. A peculiar feature is the quick rise of Fagus pollen up to 30%. The pollen curves of Plantagolanceolata, Rumex and Chenopodiaceae are established in this zone.
LPAZ OS-3 (55-0 cm, Fagus-Pinusdiploxylon-Poaceae) (970 cal. yrs. BP-until present)
Pollen of Fagus attains a maximum of 50%. The contribution of Pinusdiploxylon-type declines to 15%, while pollen of Abies is scarcely found. Deciduous tree pollen increases, mainly due to Quercus 6-8%, Carpinusorientalis/Ostrya 3-4%, Corylus and Betula. Pollen of Juniperus shows higher frequencies in the uppermost samples. The presence of Poaceae with 15% is accompanied by pollen of Artemisia, Brassicaceae, Apiaceae, Secale, etc.
Peat bog Osogovo 2 (site 29)
This small peat bog is located at 1620 m on a southwestern slope near to peat bog Osogovo 1 in a completely deforested area, nearby the tourist hut Trite Buki. Stands of beech are seen in the neighborhood (Tonkov, 1994).
<italic>Coring, lithology and radiocarbon dating</italic>
The core 95 cm long was collected with Dachnowsky hand-corer equipment. The sediment is composed of Cyperaceae peat. The single radiocarbon date confirmed that the accumulation of peat has started c. 1200 cal. yrs. BP (Table 25).
<italic>Pollen analysis</italic>
Pollen analysis was performed at 5 cm interval and a percentage pollen diagram is constructed (Fig. 94). On the pollen diagram two local pollen assemblage zones (LPAZs) are recognized (OS-2 and OS-3). Brief descriptions are as follows:
6E2204C6-F3C7-586A-BD2B-4294A1478F81
Percentage pollen diagram of Peat bog Osogovo 2.
https://binary.pensoft.net/fig/1672964
LPAZ OS-2 (95-63 см, Pinusdiploxylon-Fagus-Abies)
Pollen of Pinusdiploxylon-type dominates with over 60%, accompanied by Abies 19%, Fagus 10-20% and Quercus 3%. Pollen of deciduous tree taxa such as Carpinusbetulus, Carpinusorientalis/Ostrya, Corylus, Ulmus and Tilia is sporadically found. Among the herbs Poaceae reaches 10% while single finds of pollen of Apiaceae, Achillea-type, Dianthus-type, Cirsium-type, Scabiosa, etc. are registered.
LPAZ OS-3 (63-0 см, Fagus-Pinusdiploxylon-Poaceae)
The pollen curve of Fagus rises steeply up to 70% and a decline for Pinusdiploxylon-type to 14% is observed. The uppermost pollen spectra reveal a reverse situation with a quick decline of Fagus and some restoration for Pinusdiploxylon-type with 40%. Pollen of Quercus, Alnus, Betula, Carpinusorientalis/Ostrya is present each with 3-4%. The second maximum of Poaceae 15% is recorded.
Peat bog Begbunar (site 30)
The third peat bog is located at 1750 m (42°08’51.62”N, 22°32’45.05”E) near a spring on a northwestern slope which continues into a steep, deep ravine where stands of beech grow. Not far to the north are visible scattered groups of Pinussylvestris and Juniperussibirica (Lazarova et al., 2009, 2015) (Figs 3 and 95).
5B37C200-3B18-55D1-9EAC-7AB7323F0D7A
A view of Peat bog Begbunar (Photo: S. Tonkov).
https://binary.pensoft.net/fig/1672965
<italic>Coring, lithology and radiocarbon dating</italic>
A core 105 cm long was collected with Dachnowsky hand-corer equipment from a less densely vegetated area of the bog surface. The lithology of the sediments is: 0-75 cm Cyperaceae-Sphagnum peat, 75-105 cm Cyperaceae peat with sand. The radiocarbon age of Carex fruits and charcoal, extracted from 3 bulk sediment samples, was determined and the results are shown in Table 25. The age of the core is assigned to c. 5000 cal. yrs. BP.
<italic>Pollen analysis</italic>
Pollen analysis was performed at 5 cm interval and a percentage pollen diagram is constructed. On the pollen diagram three local pollen assemblage zones (LPAZs) are delimited (BB-1 to BB-3) (Figs 96 and 83). Brief descriptions are as follows:
E7F398EE-8997-5EEC-A678-647E0869B548
Percentage pollen diagram of Peat bog Begbunar.
https://binary.pensoft.net/fig/1672966
LPAZ BB-1 (105-72 cm, Abies-Pinusdiploxylon-Betula) (~5000-3300 cal. yrs. BP)
Pollen of Abies with 13-3% prevails, followed by Pinusdiploxylon-type 6-12% and Betula with a peak of 26% at the transition to the next zone. The deciduous tree pollen is represented also by Corylus up to 6%, Quercus, Tilia, Ulmus each with 1-2%, Alnus and Salix. Minor quantities of pollen are recorded for Carpinusorientalis/Ostrya, Carpinusbetulus, Fagus, Fraxinus and Acer. Pollen of Juglans is present throughout the entire core. The herb pollen taxa are represented by Poaceae 13-43%, Ranunculaceae up to 6%, Achillea-type up to 6%, Rumex 5%, Cichoriaceae up to 4%, etc. The constant presence of Polypodiaceae spores is between 2% and 11%.
LPAZ BB-2 (72-33 cm, Pinusdiploxylon-Fagus) (3300-900 cal. yrs. BP)
The abundance of Pinusdiploxylon-type pollen is 15-29%, accompanied by a gradual rise of Fagus pollen curve up to 20%. Pollen of Abies almost disappears in this zone. High pollen frequencies up to 40% are established for Poaceae. Pollen of Rosaceae, Fabaceae, Ranunculaceae and Achillea-type each reaches 3-4%. The pollen curve of Cyperaceae rises to 22%.
LPAZ BB-3 (33-0 cm, Fagus-Pinusdiploxylon-NAP) (900 cal. yrs. BP-until present)
Pollen of Fagus attains a maximum of 21%, while Pinusdiploxylon-type declines to 15%. In the uppermost pollen spectra Quercus, Carpinusorientalis/Ostrya and Carpinusbetulus rise to 5%, 2% and 1.5%, respectively. The maximal values for Poaceae 42%, Plantagolanceolata 19%, Cichoriaceae 2%, Rosaceae and Ranunculaceae each with 7% are characteristic for this zone. Cyperaceae pollen is 20% with a maximum of 32%.
<italic>Plant macrofossil analysis</italic>
Plant macrofossils and charred wood fragments (> 2 mm) were studied complimentary to pollen analysis. Subsamples for macrofossil analysis with a sediment volume of 50 ml were taken at every 5 cm. The material was sieved through meshes of 0.4 and 0.16 mm holes. The results of the analysis are presented as absolute numbers of determinable items (needles, seeds, nutlets, etc.) on a plant macrofossil diagram (Fig. 97). The remains of vegetative parts such as stems, leaves and others are not quantified but their presence is indicated with dots. Two local macrofossil assemblage zones (LMAZs) are distinguished (BM-1 and BM-2). Brief descriptions are as follows:
F6FE3B30-C25B-50DC-9940-3DB64B2B2FC3
Plant macrofossil diagram of Peat bog Begbunar.
https://binary.pensoft.net/fig/1672967
LMAZ BM-1 (95-55 cm) (~5000-2300 cal. yrs. BP)
In the lower part of the core the prevailing material is charred wood from Acer sp., Fraxinus, Alnus, Prunoideae/Maloideae. Also, charred wood particles from Fagus, Pinus sp. and from undeterminable conifers are found. Charred leaf fragments of Pinus sp. are present too. The interval 70-55 cm shows an abundance of fruits/seeds and vegetative parts from several semi-shrubs (Bruckenthaliaspiculifolia, Vacciniummyrtillus, Genistacarinalis) and herbs (Hypericum, Carex and Juncus species).
There are only occasional finds of undeterminable charred wood (0.2-2 mm). Most abundant are nutlets from Vacciniummyrtillus, fruits from Carexechinata, Genistacarinalis and Scirpussylvaticus. Nutlets and seeds from Potentilla and Hypericum species are also determined. Vegetative parts from Drepanocladus sp. are present in addition to those from Poaceae, Cyperaceae and Sphagnum.
8.3 Vegetation history in the Osogovo Mountain
The paleoecological information from the analyzed peat profiles, in conjunction with the radiocarbon dates, reveals the vegetation development in the central part of the Osogovo Mountain during the last 5000 years. The oldest pollen spectra indicate that the high mountain slopes and flat ridges were covered by coniferous forests dominated by Abiesalba and pines (Pinussylvestris, Pinusnigra) with an undergrowth of ferns and sciophilous herbs. The share of each tree in these forests is difficult to be estimated bearing in mind that pollen of Pinusdiploxylon-type is well known for its high pollen production and effective dispersal. The pollen grains produced by Pinusmugo are also included in the above pollen type but can not be separated by morphological features. The probable past distribution of Pinusmugo in the highest parts of mountain can be suggested but definite confirmation requires future finds of macrofossils. Regarding Abiesalba, the pollen frequencies are indicative of a considerable participation of fir in the coniferous forests c. 5000-4000 years ago. In places with high air humidity and soil moisture, such as deep ravines and river valleys, grew small populations of Fagussylvatica, while Alnus and Salix thrived along streams and brooks. The broadleaved tree vegetation, composed of Quercus, Corylus, Carpinus, Tilia, Fraxinus, Acer and Ulmus species was distributed at lower altitudes. A local expansion phase of Betula which lasted for c. 1000 years (4200-3300 cal. yrs. BP) (pollen zone BB-1, Fig. 96) indicates that openings in the forests took place thus preceding the beginning of the invasion of beech. The palynological reconstruction of the vegetation in the study area is supported by the finds of plant macrofossils such as needles and charcoal from Pinus sp. and undeterminable small charcoal fragments from conifers. The charcoal fragments from deciduous trees (Acer sp., Fraxinus, Maloideae) suggest that they climbed higher compared to the present-day situation. The charcoal particles of different size point also to local and regional fires (zone BM-1, Fig. 97).
The surface area of the Peat bog Begbunar was covered by various Juncus, Carex and Sphagnum species. Following the second peak of the macrocharcoal fragments c. 3200-3000 cal. yrs. BP, the appearance of macrofossils from heliophilous taxa such as Genistacarinalis, Vacciniummyrtillus and Bruckenthaliaspiculifolia was most probably connected with increased opening of the landscape in the nearby surroundings. This picture of the vegetation cover on the high central parts of the mountain for the time interval 5000-3500 cal. yrs. BP is identical with the results from the Peat bog Osogovo 1.
Indications of human activity are noticed already c. 5000 cal. yrs. BP when pollen of Secale and Triticum-type was deposited, alongside with the presence of pollen from Rumex and Plantagolanceolata. On the other hand, in the sediments of Peat bog Osogovo 1, the appearance of Secale pollen starts much later c. 1300 cal. yrs. BP (Fig. 93). This observation probably reflects local/regional specific features of human activity. For example, the high quantities of Scleranthus pollen, indicative of stockbreeding, are recorded in the above site with a first maximum assigned to the onset of the Late Bronze Age. Around 2700 cal. yrs. BP a peak in the presence of the anthropogenic indicators is registered, quite probably associated with the local Thracian tribes which moved higher up in the mountains surrounding the Struma river valley (Bozhkova, Delev, 2002).
The next stage in the development of the vegetation cover in the Osogovo Mountain lasted between 3300 and 900 cal. yrs. BP (pollen zone OS-2, Figs 93 and 94). Important changes in the forest composition took place as in the course of a thousand years populations of Fagussylvatica gradually overcame the conifers, mostly Abiesalba on many areas, thus shaping a belt of monodominant or mixed communities. The reasons for this replacement were likely of a complex character, including a change towards a more humid and cooler climate with lower average temperatures, but also aided by human interference in the forest cover. The expansion of Fagussylvatica populations in Europe in Late Holocene often coincides with disturbance events, which may be climatic or anthropogenic in nature (Bradshaw et al., 2010; Bradshaw, Sykes, 2014). For example, the examination of the relationship between pollen percentage values and charcoal data from southern Scandinavia has shown that charcoal values were generally higher immediately prior to local beech establishment (Bradshaw, Lindbladh, 2005). Similarly, the macrofossil diagram from the Peat bog Begbunar comprises a peak of charcoal fragments including such identified as Fagusc. 3300-3000 cal. yrs. BP (zone BM-1, Fig. 97). These finds precede the invasion of beech and are supported by a rise of Fagus pollen values. Human impact may have been an important local factor in tree population expansion from presence to dominance but it cannot fully explain the pattern of the Late Holocene beech population expansion in Europe (Giesecke et al., 2007).
The first maximum of beech in the Osogovo Mountain was reached c. 1000 cal. yrs. BP as visible in all pollen diagrams. The final advance of Fagus occurred a couple of centuries ago and was quite probably primarily controlled by climatic change.
The rather uniform content of the macrofossil record after c. 2200 cal. yrs. BP (zone BM-2, Fig. 97) and the nearly complete lack of charcoal fragments suggest that vast areas were already deforested and the openings were colonized by semi-shrubs and herbs. The forests served as an important source for wood used for construction purposes, heating and metallurgy. The local economy flourished as the Romans introduced advanced methods for the cultivation of the fields (Bozilova et al., 1994). Since this period the cultivation of walnut in the area has become widespread, as evidenced by the continuous pollen curve of Juglans (Fig. 96). After 720 cal. yrs. BP, and particularly since 400 cal. yrs. BP, the impact of humans on the natural woods was intensified as demonstrated by the decline of the pollen curves of Pinusdiploxylon-type and Fagus, and the increase of Poaceae, Juniperus and Plantagolanceolata pollen. The destruction of the woods resulted also in the enlargement of the areas for summer pasture land and the present-day appearance of the vegetation cover.
During the last centuries the general trend of the vegetation development in the Osogovo Mountain witnessed a progressive large-scale degradation of the woodlands. The destruction of the remnants of the pine forests culminated in their fragmentary state within the beech belt, above it, or in isolated and inaccessible places. The beech forests were also subjected to exploitation which resulted in the artificial lowering of the timber-line at many places. The peat bogs investigated were already situated in the treeless zone above the beech forests. The open areas were occupied by diverse herb communities composed of Poaceae, Ranunculaceae, Rosaceae, Fabaceae, Caryophyllaceae and Apiaceae species. Until the last decades intensive cattle-breeding was practiced, as proven by the presence of a large number of anthropogenic pollen indicators such as Cichoriaceae, Plantagolanceolata, Rumex, Urtica, etc. Nowadays, the absence of grazing is the main reason for the spontaneous restoration of Pinussylvestris on some terrains. Parallel to these changes, signs of a partial enlargement of hornbeam and mixed oak communities are visible at lower altitudes.
In summary, the pollen and plant macrofossil analyses showed that the vegetation cover of the Osogovo Mountain featured important transformations over the last 5000 years. A coniferous belt composed of Abiesalba and Pinus existed at high altitudes and below it were distributed oak forests with Carpinus, Tilia, Fraxinus, Acer and Ulmus. The replacement of the coniferous forests by beech started c. 3200 cal. yrs. BP and was of complex character, promoted by factors related to both climate change and anthropogenic disturbance. The remnants of the coniferous forests and also the monodominant or mixed communities of beech were subjected to destruction during the last centuries.
9. MALESHEVSKA MOUNTAIN9.1 Physico-geographical characteristics and modern vegetation
Maleshevska Mountain (peak Iljov vrah, 1802 m) is part of the Osogovo-Belasitsa mountain range. The ridge of the mountain is a highly curved arc, projecting to the south, along the state border with the Republic of North Macedonia (Fig. 2). Most of its eastern part remains within Bulgaria and covers an area of c. 497 km2. In general, the mountain resembles an isosceles triangle with its tip facing west. To the east, the slopes descend steeply to the Kresna gorge of the Struma river and the northern part of the Sandanski-Petrich Basin, which separates it from the Pirin Mountain. To the west it borders the southeast, south and southwest of the Maleshevo historical and geographical area. To the north the saddle Chetalo (1619 m) connects it with the Vlahina Mountain and the valley of the Sushichka river, a right tributary of the Struma river. To the south the valley of the Lebnitsa river, a right tributary of the Struma river separates it from the Ograzhden Mountain. Gradually to the south the ridge of the mountain decreases (Todorov et al., 2016).
The mountain has a complex geological structure. The geology of the area is related to the distribution of some major types of metamorphic, magma and sedimentary rocks. The metamorphic rocks are of pre-Cambrian age, represented by biotite and bivalve gneisses and migmatites, accounting for about 60% of the territory. Granites are found in the northeastern parts and in the valley of the Lebnitsa river, spots of volcanic rocks in the highest denudation surfaces and in the lowest places. Paleogene, Neogene and Quaternary sediments are also encountered (Zagorchev, 2001).
The mountain falls in the Continental-Mediterranean climate region. The average annual temperature in the foothills is 14°C, and at an altitude of 1700-1800 m is 5°-6°C. The average annual precipitation is also vertically and horizontally differentiated. In the southern and lower parts of the mountain it is 500-600 mm with a maximum in November, at an altitude of 600-1000 m it is 700-800 mm with a maximum in October, and above 1000 m it is 1000 mm with a maximum in May (Velev, 2010).
The southwestern, southern and eastern slopes of the mountain belong to the catchment area of the Struma river and are drained by its right tributaries. The northwestern slopes facing the Maleshevo region belong to the Vardar river basin. The rivers in the mountain have rain-snow feeding with winter-spring high water and summer-autumn low water (Todorov et al., 2016).
The most widespread are the leached cinnamon forest soils (Chromic Luvisols) up to 700 m and brown mountain forest soils (Distric Cambisols) up to 1600-1700 m. The former is characteristic of the oak belt and the latter of the beech belt and the remnants of the coniferous forests. Mountain meadow soils (Humic Umbrosols) are developed above the upper timber-line. The erosion is ubiquitous, especially in the lower parts of the mountain (Ninov, 1997).
According to the last geobotanical zoning Maleshevska Mountain is included as a separate region in the Western Bulgarian Border Mountain District of the Illyrian (Balkan) Province (Bondev, 2002). The combination of the geographical location, climatic, soil and hydrological conditions has influenced the character of the modern vegetation, expressed in the presence of rare and southern elements, as well as a clear distribution in three vertical belts. The first belt of the xerothermic oak forests is well separated on the southeast and eastern slopes up to 500-600 m. It is composed of the communities of Quercuspubescens, Quercusfrainetto, Carpinusorientalis, Paliurusspina-christi, etc. In this belt, above the village of Kamenitsa, there are communities of the evergreen oak Quercuscoccifera. Other mediterranean elements are also found such as Juniperusexcelsa, Phillyrealatifolia and Jasminumfruticans. The riparian associations of Platanusorientalis are also characteristic. In the belt of the mesophilous and xeromesophilous oak and hornbeam forests (600-900 m) the basic plant communities are those of Quercusdalechampii and Ostryacarpinifolia. They include also Carpinusbetulus, Fraxinusornus and Acerpseudoplatanus. Groups of Pinusnigra are also found. The beech forest belt is very well developed and relatively compact above 900-1000 m. These forests are usually monodominant but, in their composition, participate also Abiesalba, Abiesborisii-regis, Betulapendula, Populustremula, Pinusnigra and Pinussylvestris. The flattened ridges are characterized by the spread of high-mountain species and fragments of communities of Vacciniummyrtillus, Vacciniumuliginosum, Chamaecytisusaustriacus, Bruckenthaliaspiculifolia, etc. (Velchev, Tonkov, 1986)
9.2 Study sitePeat bog (site 31)
This peat bog is located at 1720 m (41°43’14.31”N, 23°02’08.88”E) in a treeless area near a spring on an east-facing slope above the timber-line shaped by the beech forests. It occupies a small area of about 50 m2 (Figs 3 and 98). The locality was used in former times as mountain pasture land. The bog vegetation is composed of Agrostistenuis, Deschampsiacespitosa, Carexechinata, Eriophorumlatifolium, Bistortamajor, Potentillaerecta, Armeriarumelica, Veratrumlobelianum, Scleranthus perennis, Bruckenthaliaspiculifolia, etc. (Tonkov, Bozilova, 1992a).
3648BAD6-BBEE-523F-9172-B8BA5914A87F
A view of the Peat bog in the Maleshevska Mountain (Photo: S. Tonkov).
https://binary.pensoft.net/fig/1672968
<italic>Coring, lithology and radiocarbon dating</italic>
A sediment core 205 cm long was recovered with Dachnowsky hand-corer equipment. The lithology of the sediments is: 0-180 cm Cyperaceae peat, 180-205 cm peat with sand. The radiocarbon age of 3 bulk sediment samples was determined and the results are shown in Table 26. The age of the core is estimated at c. 8000 cal. yrs. BP.
Radiocarbon dates from the peat bog in the Maleshevska Mountain.
Lab. code
Depth (cm)
14C age (BP)
14C age cal. BP, ±2σ (mid-point)
Material dated
Hv-11347
26-29
2650±105
2380-3010 (2695)
peat
Hv-11349
85-89
3205±185
2950-3900 (3425)
peat
Hv-11487
171-180
6535±105
7250-7600 (7425)
peat
<italic>Pollen analysis</italic>
Pollen analysis was performed at 5 cm interval and a percentage pollen diagram is constructed. On the pollen diagram three local pollen assemblage zones (LPAZs) are delimited (ML-1 to ML-3) (Figs 99 and 83). Brief descriptions are as follows:
940899B8-4802-5800-B26D-BA453AE6DCE9
Percentage pollen diagram of the Peat bog in the Maleshevska Mountain.
LPAZ ML-1 (205-115 cm, Abies-Pinusdiploxylon-Quercetum mixtum) (~8000-4500 cal. yrs. BP)
High pollen values are recorded for Abies 35-50% and Pinusdiploxylon-type 37%. Pollen of Quercus 24%, Carpinusbetulus 7%, Alnus up to 5%, Corylus, Tilia, Ulmus, Carpinusorientalis/Ostrya and Humulus/Cannabis-type is also present. Single pollen grains of Rhamnus/Paliurus-type, Jasminum and Hedera are determined. The variety of herb pollen taxa is considerable, represented by Poaceae 13-15%, Apiaceae up to 8%, Cichoriaceae 2%, Chenopodiaceae, Ranunculus-type, Artemisia, Cyperaceae 9%, etc.
LPAZ ML-2 (115-42 cm, Pinusdiploxylon-Abies-Fagus) (4500-2800 cal. yrs. BP)
The pollen curve of Abies declines to 3% and rises again to a second maximum of 24% (level 80 cm). Pollen of Pinusdiploxylon-type is present with 50%. The most characteristic feature is the appearance of the pollen curve of Fagus with 5%. The rest of the deciduous tree taxa, with the exception of Quercus 12%, are present with less than 2%. It is worth to mention the first records of Juglans, Castanea, Phillyrea and Vitis pollen. The pollen curve of Poaceae varies between 10% and 23%, followed by Scleranthus and Cirsium-type with 7% and 5%, respectively. Pollen of Polygonumaviculare-type, Plantagolanceolata, Urtica, etc. is also found.
LPAZ ML-3 (42-0 cm, Fagus-Pinusdiploxylon) (2800 cal. yrs. BP-until present)
Pollen of Pinusdiploxylon-type is present with 55-25%. The pollen curve of Abies reaches its last maximum of 11% and declines. The most characteristic feature is the rise of Fagus pollen curve up to 30-33%. Pollen of Quercus participates with 10-5%, together with Carpinusbetulus, Carpinusorientalis/Ostrya, Corylus, Alnus. Pollen grains of Juglans and Castanea are determined in all samples. The frequencies of the herb pollen taxa slightly increase, represented by Poaceae 12%, Scleranthus 11%, Cichoriaceae 8%, Artemisia 6%, Plantagolanceolata 3%, Cirsium-type, Polygonumaviculare-type, Rumex, Filipendula, Cyperaceae 7%, etc.
9.3 Vegetation history in the Maleshevska Mountain
The formation of the investigated peat bog started about 8000 years ago when forests of Abies with admixture of pines (Pinussylvestris, Pinusnigra) dominated the landscape and shaped also the timber-line. The wide distribution of the conifers was favored by an increase in precipitation and air/soil humidity during the Holocene climatic optimum, proved also by the find of pollen of Hedera and Humulus/Cannabis. The peat bog was included in the upper part of the coniferous belt and on more open places developed stands of Juniperus. Groups of Alnus were found along the mountain streams and brooks. Small populations of Fagus and Betula were also present. Below the coniferous belt were distributed mixed oak forests (Quercetum mixtum) with abundant Tilia, Ulmus, Carpinusbetulus and Corylus. The pollen assemblages contain irregular, small quantities of anthropogenic pollen taxa such as Plantagolanceolata, Rumex, Scleranthus which indicate that the intensity of the human impact on the natural vegetation was still rather low, at least in the high mountain areas (pollen zone ML-1, Fig. 99). The presence of the above-mentioned pollen taxa is considered as an indication of ruderal communities along forest paths (Behre, 1981; Bozilova, Tonkov, 1990). The find of Cerealia-type pollen might reflect the initial cultivation of cereals in this part of the Struma river valley.
Substantial changes in the composition and distribution of the forest vegetation occurred after c. 4500 cal. yrs. BP. Particularly notable was the quick decline of the areas occupied by Abies and the increase of Pinus. It is likely, that a decrease in air humidity and human intervention may have limited the spread of Abies forests. Changes also occurred in the deciduous forests, facing lower participation of Corylus, Ulmus, Carpinusbetulus, Ostryacarpinifolia and Carpinusorientalis. Quite probably, the upper boundary of the oak belt also descended, from where a narrow strip of Fagus began to form, or the distribution of beech was mosaic in places previously occupied by Abies and Carpinusbetulus. Mixed coniferous-beech communities already existed as Fagus was invading new areas due to its better growth and renewal opportunities. At the same time evidence of almost continuous presence of Juglans and Castanea appeared in the pollen record (pollen zone ML-2, Fig. 99).
Around 2800 cal. yrs. BP a heavy destruction of the woody vegetation has occurred, affecting both the deciduous and coniferous forests in the mountain. Undoubtedly, the reason was the anthropogenic factor, confirmed by the increased amount of pollen from plants such as Scleranthus, Cichoriaceae, Polygonumaviculare, Urtica. It is assumed that the peat bog was already situated above the timber-line.
The last period of vegetation history is related to the formation of the modern altitudinal belt differentiation. As a result of its rapid spread, Fagus has become the dominant tree and formed a belt between 1000 and 1700 m. The distribution of the beech forests ended the dominance of the conifers and led to their restriction as separate stands only in inaccessible places. On one hand, the cooling at the beginning of the Subatlantic proved to be conducive to beech, and on the other, the process of its rapid enlargement was aided by humans. Extensive areas were cleared for livestock breeding and the coniferous wood was preferred material for burning and construction activities. This is proved by the increasing participation of cultivated cereals and antropophytes such as Plantagolanceolata, Rumex, Scleranthus and other herbs. There is a substantial decrease in the areas occupied by the oak forests which were exploited by the local people on easily accessible slopes. In their place, secondary communities of Quercuspubescens and Carpinusorientalis settled on eroded terrains (pollen zone ML-3, Fig. 99).
The location of the peat bog was already away from the beech forests and grasslands spread over vast areas around it. In recent centuries, the local people started to exploit also the beech forests which nowadays in some places are already thinned out and filled against erosion processes with artificial plantations of Pinussylvestris.
10. VLAHINA MOUNTAIN10.1 Physico-geographical characteristics and modern vegetation
Vlahina Mountain (peak Ogreyak, 1924 m) is part of the Osogovo-Belasitsa mountain range. It extends from north to south about 50 km and its width varies from 12 km north to 30 km south. A section of the state border between Bulgaria and the Republic of North Macedonia crosses the ridge. Most of the mountain area remains on Bulgarian territory. It is bordered on the northwest by the Osogovo Mountain (the Black Rock saddle, 930 m), on the south by the Maleshevska Mountain (the saddle Chetalo, 1619 m), and on the east and west by the valleys of the Struma and Bregalnitsa rivers. (Fig. 2) The ridge of the mountain is flattened, its slopes to the east sloping, and to the west steeper. The mountain is composed mainly of metamorphic rocks (gneisses, amphibolites) but also of metamagmatites, granites, limestones, marls, etc. (Zagorchev, 2001).
The mountain falls in the Continental-Mediterranean climate region. The average annual temperature is 11°C, the average temperature amplitude is 21°C, the average annual rainfall is 700 mm with a maximum in the autumn and a minimum in summer (Velev, 2010). Climatically, the mountain is characterized by approximately equal amounts of winter rainfall and summer rainfall, which tends to equalize the mediterranean with the continental climatic influence (Tishkov, 1976).
The predominant soils in the lower parts are leached cinnamon forest (Chromic Luvisols), followed by brown mountain forest soils (Distric Cambisols) and above the timber-line are distributed mountain meadow soils (Humic Umbrosols). The spread of shallow soils (Umbric Leptosols) is highly significant and deluvial soils (Colluviosols) occur in some sections. As a result of active erosion processes regosols (Regosols) are also quite widespread (Ninov, 1997; Todorov et al., 2014).
According to the last geobotanical zoning Vlahina Mountain is included as a separate region in the Western Bulgarian Border Mountain District of the Illyrian (Balkan) Province (Bondev, 2002) but due to the narrow morphographic connection to the south with the Maleshevska Mountain and the slight difference in their altitudes, the same vegetation belts are observed (Velchev, Tonkov, 1986; Bondev, 2002). The vegetation of each of the mountains has certain features that should be taken into account. For example, in the belt of the xerothermic oak forests, well distinct on the eastern and northeastern slopes of the Vlahina Mountain, there are no characteristic mediterranean species like Quercuscoccifera. The communities of Carpinusbetulus in the northern part of the mountain are relatively compact. The beech forests also include Betulapendula, Populustremula, Abiesalba, Pinussylvestris. Of particular interest are the mixed communities of beech with Pinusnigra preserved above the village of Gabra and below peak Momina Skala at 1200 m. Compared to the Maleshevska Mountain, the ridges are characterized by widespread distribution of fragments from the communities of Chamaecytisusaustriacus, Juniperuscommunis, Vacciniummyrtillus, as well as of a number of high mountain species (Kitanov et al., 1986).
10.2 Study sitesPeat bog Kadiytsa (site 32)
This peat bog is located at 1700 m near a small stream in a vast deforested area, above the beech forests, south of peak Kadiytsa, at an area of about 150 m2 (Fig. 3). The scarce tree vegetation is represented by separate groups or single trees of Pinussylvestris and Juniperuscommunis. The bog vegetation is composed of Carexechinata, Eriophorumlatifolium, Bistortamajor, Potentillaerecta, Geummontanum, Ranunculusmontanus, Filipendulaulmaria, Veratrumalbum, etc. (Tonkov, 1992).
<italic>Coring and lithology</italic>
The thickness of the peat layers varies between 40 and 80 cm, and at some places it reaches 100-120 cm. The core is 110 cm long and was recovered with Dachnowsky hand-corer equipment. The sediment consists of Cyperaceae peat mixed with vegetative plant remains. The attempts to obtain radiocarbon dates were not successful.
<italic>Pollen analysis</italic>
Pollen analysis was performed at 5 cm interval and a percentage pollen diagram is constructed (Fig. 100). On the pollen diagram two local pollen assemblage zones (LPAZs) are delimited (K-2 and K-3) which are correlated with the palynostratigraphy from the peat bog in the Maleshevska Mountain. Brief descriptions are as follows:
4EE30592-0A72-58E1-A2FB-DE724837A33B
Percentage pollen diagram of Peat bog Kadiytsa.
https://binary.pensoft.net/fig/1672971
LPAZ K-2 (110-37 cm, Pinusdiploxylon-Abies-Fagus)
The total tree pollen dominates with 80%, contributed by Pinusdiploxylon-type 62-68%, Abies 20%, Quercus, Corylus, Alnus and Juniperus each with 2-7%. Pollen of Juglans and Syringa is also determined. From the herb pollen taxa can be mentioned Poaceae 2-8%, Cichoriaceae 4%, Apiaceae, Scleranthus, Cirsium-type, etc. The anthropogenic pollen taxa like Cerealia-type, Plantagolanceolata, Rumex are present sporadically. The curve of Polypodiaceae spores reaches 10%.
LPAZ K-3 (37-0 cm, Fagus-Pinusdiploxylon-NAP)
The tree pollen taxa participate with low values with the exception of Pinusdiploxylon-type 60-75%. The pollen curve of Fagus reaches 15%. Pollen of Juglans is recorded in all samples. The total herb pollen is 25%, contributed by Poaceae 10%, Scleranthus 5%, Cichoriaceae 3%, Plantagolanceolata, Cichoriaceae, etc. Spores of Polypodiaceae are sporadically found.
Swamp Obel (site 33)
This smal swamp with a triangular shape is located near the village of Obel at 955 m (41°58’07.36”N, 22°55’32.21”E) on the right side of the road Blagoevgrad-Delchevo and occupies an area of 0.87 ha (Fig. 3). It is fed by a karst spring and condensation waters from the surrounding hills. In the direction to the nearby neighborhood Klisura it is surrounded by arable land and to the east and north it borders coppice woods of Quercuspubescens, Quercuscerris and Carpinusbetulus. In their composition are found also Fagussylvatica, Carpinusorientalis, Acerplatanoides, Acercampestre. The vegetation of the swamp and around it is represented by Potamogetonnatans, Sparganiumerectum, Irispseudacorus, Alismaplantago-aquatica, Heleocharispalustris, Menthaaquatica, Galiumpalustris, Lythrumsalicaria, Gratiolaofficinalis, Potentillareptans, Prunellavulgaris, etc. (Tonkov, 1992). In 2012 the locality with the swamp was declared a protected teritorry Blatoto (Fig. 101).
4B060638-1362-59B8-A5E9-5B0A7B1CF6D8
A view of Swamp Obel (source: svetlimesta.com).
https://binary.pensoft.net/fig/1672972
<italic>Coring and lithology</italic>
The sediment core is 110 cm long and was recovered with Dachnowsky hand-corer equipment from the peripheral western part of the swamp at water depth of 0.5 m. The sediment is clay. The attempts to obtain radiocarbon dates were not successful.
<italic>Pollen analysis</italic>
Pollen analysis was performed at 5-10 cm interval and a percentage pollen diagram is constructed (Fig. 102). On the pollen diagram three local pollen assemblage zones (LPAZs) are delimited (Ob-1 to Ob-3). Brief descriptions are as follows:
The total tree pollen dominates with 75-90%, contributed by Pinusdiploxylon-type 80-40%, followed by Quercus 10-15%, Salix 5% (21% at level 75 cm), small quantities of pollen from Juniperus, Alnus, Fagus, Corylus and traces of Acer, Carpinusbetulus, Juglans, and Vitis. The herb pollen taxa are represented by Poaceae 10%, Polygonumaviculare-type 5%, Cichoriaceae, Achillea-type and Chenopodiaceae each below 5%, Scleranthus, Brassicaceae, etc. The hygrophytes and hydrophytes are represented by Cyperaceae, Typha/Sparganium-type, Typhalatifolia 10%, Lemna 8%.
LPAZ Ob-2 (72-42 cm, Pinusdiploxylon-NAP-Quercus)
This zone is characterized by the abundance of herb pollen taxa such as Poaceae with a maximum of 35% (level 45 cm), Cichoriaceae 5%, Chenopodiaceae 5%, Brassicaceae, a number of anthropogenic taxa (Cerealia-type, Triticum-type, Centaureacyanus, Plantagolanceolata, Urtica). Tree pollen is represented by Pinusdiploxylon-type up to 60% with a steep decline at the transition to the next zone, Quercus with minimal values of 5-7%, the appearance of continuous pollen curves of Juniperus, Fagus, Ulmus, Carpinusbetulus, Carpinusorientalis/Ostrya. Juglans pollen is also present. Pollen of Lemna, Typhalatifolia, Alisma and Iris is determined.
LPAZ Ob-3 (42-0 cm, Quercus-Fagus-Carpinus)
The transition to this zone is clearly marked by decline of the total tree pollen to 30%. Subsequently, the participation of tree taxa increases again, contributed by Quercus up to 27%, Juniperus 6%, Carpinusorientalis/Ostrya 7%, Carpinusbetulus 4%, Ulmus, Alnus and Salix each with 4%. In the uppermost samples pollen of Fagus reaches 7% and Pinusdiploxylon-type 20-25%. Among the herb pollen taxa a steady presence for pollen of Poaceae 7-10%, Chenopodiaceae 5%, Cichoriaceae 5%, Achillea-type 3% is recorded. Notable is the continuous participation of pollen from Triticum-type, Polygonumaviculare-type, Urtica, Rumex and Scleranthus. The hygrophytes and hydrophytes are represented by pollen of Cyperaceae, Typha/Sparganium-type, Lemna and Potamogeton.
10.3 Vegetation history in the Vlahina Mountain
The age of the bottom part of the core from Peat bog Kadiytsa is provisionally estimated at c. 4700 cal. yrs. BP (pollen zone K-2, Fig. 100) when compared with the core from the Maleshevska Mountain (pollen zone ML-2, Fig. 99). The time when sedimentation in the Swamp Obel started is difficult to determine but the palynostratigraphy suggests that most probably the core spans the last c. 2000-1500 years.
Several thousand years ago in the southern high part of the Vlahina Mountain coniferous forests of Pinus and Abies were distributed. Large areas were occupied by monodominant or mixed communities of Abies in which the herb layer was composed of shade-tolerant species including ferns. In the oak forests below the coniferous belt were found Tilia, Corylus, Carpinusorientalis and Ostryacarpinifolia. Small groups or populations of Fagus and Carpinusbetulus were distributed in places between the oak and the coniferous forest belts. The relatively high percentage of Alnus pollen can be explained by the presence of stands near streams. The herb communities occupied small areas and were composed mainly of Poaceae, Apiaceae, Cichoriaceae, Lamiaceae, Asteraceae and Ranunculaceae species.
Around 2800 cal. yrs. BP a substantial change in the forest cover occurred, characterized by the almost complete disappearance of Abies and the enlargement of the areas occupied by Pinus. The expansion of Fagus was preceded by a short-term increase of herbs (pollen zone K-3, Fig. 100).
The next period of vegetation development in the mountain marked the widespread of the beech forests in place of the conifers. As a result, only separate groups of pines (Pinussylvestris and Pinusnigra) were preserved inside the beech forest belt or above it.
At lower altitudes the destructions in the oak forest belt resulted in the increase of the herb vegetation with a significant presence of the anthropogenic pollen taxa such as Triticum-type, Cerealia-type, Secale, Plantagolanceolata, Rumex, Polygonumaviculare, Cichoriaceae, Chenopodiaceae. The pollen diagram from Swamp Obel manifests a period of human occupation in the area (pollen zone Ob-2, Fig. 102), characterized by cultivation of crops, walnut and sweet chestnut, animal husbandry and exploitation of the forest resources for diverse uses. Later on, the arable land around the swamp was abandoned and gradually colonized by various herbs and junipers, while beech enlarged its areas. Also, a partial restoration of the oak forests with lime, elm and hornbeam took place.
In recent centuries, as a result of the permanent settlement and the diverse human activities, the natural vegetation in all altitudinal belts was destructed and replaced in many places by secondary shrub or herb plant communities.
It is essential to outline that the palynological studies in the Maleshevska and Vlahina mountains provide the most convincing evidence for the past distribution of coniferous forests in the mountains west of the Struma river. The dynamic processes in this montane region were not prolonged and the modern vegetation belt differentiation was formed also under the influence of human interference.
11. BELASITSA MOUNTAIN11.1 Physico-geographical characteristics and modern vegetation
Belasitsa Mountain (peak Radomir, 2029 m) is the southernmost part of the Osogovo-Belasitsa mountain range located in the southwestern corner of the country, south of the Strumeshnitsa river valley. The territory of the mountain is divided among Bulgaria, Greece and the Republic of North Macedonia. It extends from the Rupel gorge in the east to the Kosturinska saddle in the west about 60 km in length. On the territory of Bulgaria is located about 30% of its area, the northern slopes, and the length of this section is 33 km with an average width of 4-5 km (Fig. 2). The mountain was formed as a separate orographic unit, a linear horst, as a result of block-fractured tectonic movements during the Tertiary. The adjacent fields sank deep and the mountain rose as a block, extended east-west between two parallel faults. It is made up of amphibolites, shists, granites, gneisses, etc. The erosion along the northern faulty slope of the mountain has resulted in abundant sediment at the foot of the slope where extensive sediment cones have accumulated, arranged in a continuous plume from Petrich to Strumitsa. The highest parts of the sedimentary cones are made up of large rock blocks mixed with coarse gravel and sand. Smaller materials are located below, and the finer particles build the lowest parts of the cones, from which many springs originate (Galabov et al., 1977; Nikolov, Yordanova, 2002).
The climate in the region is Continental-Mediterranean characterized by mild winters but with frequent and sometimes heavy rainfall, and hot dry summers. The average annual temperature is 13.9°C and decreases to 3°C with increasing altitude. The average January temperatures change from 1°C in the low parts to -6°C in the highlands, and the average July temperatures from 21°C to 11°C, respectively. The average annual precipitation is 676 mm and depending on the altitude it varies from 600-700 mm at the foot of the mountain to 900 mm in the high parts. Their distribution is characterized by autumn-winter maximum and summer minimum (Koleva, Peneva, 1990; Velev, 2010).
The leached cinnamon forest soils (Chromic Cambisols) occur on the lower slopes and above 800 m up to the ridge they change to brown forest soils (Cambisols) with a low humus horizon (Ninov, 1997).
According to the last geobotanical zoning Belasitsa Mountain is included as a separate district of the Macedonian-Thracian Province (Bondev, 2002). The forested area of the Bulgarian part of the mountain is c. 10000 ha. The prevailing territory of this area is covered by native broadleaf forests (74.5 %) while the rest of it is forest plantations (25.5%). The most widespread tree species are Fagussylvatica (48.3% from the total forested area) and Castaneasativa (13.1%), followed by Pinussylvestris (6.8%) and Pinusnigra (5.9%) (Velichkov et al., 2010). The present vegetation on Bulgarian territory is distributed in several altitudinal belts. The lowermost xerothermic oak belt (up to 300-400 m) is fragmented, composed of Quercuspubescens, Quercusfrainetto, Juniperusoxycedrus, Paliurusspina-christi. Along small riverlets and brooks are found communities of Platanusorientalis. The belt of mesophilous and xeromesophilous oak and hornbeam forests (300/400-800/900 m) is characterized by the dominance of the communities of Castaneasativa. In their composition are growing also Fraxinusornus, Platanusorientalis, Ostryacarpinifolia, Coluteaarborescens, Coronillaemerus, etc. The beech forest belt (800/900-1700 m) is very well developed, formed mainly by monodominant communities of Fagussylvatica. On small areas are growing Abies bоrisii-regis and Betulapendula. Taxusbaccata and Ilexaquifolium are also found. Nowadays beech shapes the upper timber-line as a coniferous belt is lacking. Above the beech forests follows a belt of shrubby and herb vegetation composed of Juniperuscommunis, Vacciniummyrtillus, Bruckenthaliaspiculifolia, Chamaecytisusabsinthioides, Nardusstricta, Festucavalida, etc. In the lower part of this belt are growing isolated trees of Pinussylvestris. Overall, the vegetation is highly influenced by the anthropogenic activity, particularly the oak and hornbeam forests, and the communities of sweet chestnut as well (Velchev, Tonkov, 1986; Bondev, 1991).
The southern slopes on Greek territory are deforested to a large extent. Up to 1000 m are found Quercuscoccifera, Phillyrealatifolia, Pistaciaterebinthus, Quercusdalechampii, Quercuspubescens, Carpinusorientalis, and in the northeastern parts Castaneasativa. In the eastern part of the beech forests, between 1150 and 1300 m, are growing groups of Abiesborisii-regis (Stojanov, 1921; Athanasiadis et al., 2000, 2003).
11.2 Study sitesMire Gyola (site 34)
This small mire, named Gyola, is located at 714 m (41°21’17.12”N, 23°07’31.31”E) in the center of the Bulgarian part of the mountain, southwest from the village of Kolarovo. (Fig. 3). The mire occupies 0.1 ha within a forest of Castaneasativa with some admixture of Fagussylvatica, Ostryacarpinifolia, Corylusavellana, Carpinusorientalis, Juglansregia, Alnusglutinosa, Quercusdalechampii and Fraxinusornus. Planted stands of Pinussylvestris and Pinusnigra are also found nearby. The shores of the mire are overgrown by Carex sp., Alismaplantago-aquatica, Equisetumarvense, Lysimachiavulgaris, Pteridiumaquilinum, Dryopterisfilix-mas, Aegopodiumpodagraria, Plantagomajor, Poanemoralis, Brachypodiumsylvaticum, etc. (Tonkov et al., 2012; Tonkov, Possnert, 2014) (Fig. 103).
30CE8C64-5BFB-5A15-B403-ADBE9C328029
A view of Mire Gjola (Photo: S. Tonkov).
https://binary.pensoft.net/fig/1672975
<italic>Coring, lithology and radiocarbon dating</italic>
A sediment core 210 cm long was recovered from the peripheral part of the mire at water depth of 30 cm with Dachnowsky hand-corer equipment. The lithology of the sediments is: 0-80 cm yellow-brown clay with sand, 80-140 cm grey clay with sand, 140-210 cm yellow-brown clay with sand. The radiocarbon age of 4 samples of bulk sediment was determined and the results are shown in Table 27. The age of the core is estimated at c. 8500 cal. yrs. BP.
Radiocarbon dates from Mire Gyola and Peat bog Belasitsa 1.
Lab.code
Depth (cm)
14C age (BP)
14C age cal. BP, ±2σ (mid-point)
Cal. BC/AD)
Material dated
Mire Gyola
Ua-43943
30-35
507±30
630-500 (565)
1320-1450 (1385) AD
clay with sand
Ua-41527
120-126
1474±30
1410-1300 (1355)
540-650 (595) AD
clay with sand
Ua-43944
148-153
3277±30
3580-3410 (3495)
1630-1460 (1545) BC
clay with sand
Ua-41249
176-190
7099±44
8010-7840 (7925)
6060-5890 (5975) BC
clay with sand
Belasitsa 1
INRNE-112
50-70
1850±50
1900-1620 (1760)
50-330 (190) AD
peat with sand
<italic>Pollen analysis</italic>
Pollen analysis was performed at 5-10 cm interval and a percentage pollen diagram is constructed. On the pollen diagram four local pollen assemblage zones (LPAZs) are delimited (BL-1 to BL-4) (Figs 104 and 83). Brief descriptions are as follows:
306C63D9-6D6C-59A2-A5E3-35E89007959F
Percentage pollen diagram of Mire Gyola.
https://binary.pensoft.net/fig/1672976
LPAZ BL-1 (210-172 cm, Artemisia-Castanea-Poaceae) (~8500-5000 cal. yrs. BP)
The dominant pollen type is Artemisia with 45-70%, followed by Castanea 15%, Poaceae 12%, Alnus 7% and Quercusrobur-type 4%. Pollen of Juglans is present in all samples. Low percentages are recorded for Fagus, Quercuscerris-type, Pinusdiploxylon-type, Carpinusorientalis/Ostrya and various herbs.
LPAZ BL-2 (172-130 cm, Castanea-Artemisia-Pinusdiploxylon-Poaceae) (5000-2000 cal. yrs. BP)
The pollen curve of Castanea rises to 50%, while Artemisia declines to 10%. Other pollen taxa which can be mentioned are Pinusdiploxylon-type 10%, Poaceae 15%, Alnus 7%, Cichoriaceae, Chenopodiaceae, Polygonumaviculare-type and Dianthus-type each below 5%.
LPAZ BL-3 (130-42 cm, Castanea-Pinusdiploxylon-Poaceae) (2000-650 cal. yrs. BP)
Pollen of Castanea continues to dominate with 50-60%, accompanied by Pinusdiploxylon-type 10-15%, Alnus 10-5%, minor quantities of Fagus, Abies, Corylus, Carpinus and Juglans pollen. The herb pollen taxa are represented by Poaceae 15%, Artemisia 8%, Polygonumaviculare-type-7%, Cichoriaceae 6%, Apiaceae, Plantagolanceolata, etc. Pollen of Cyperaceae 5%, spores of Polypodiaceae 3% and Pteridium 4% are determined.
LPAZ BL-4 (42-0 cm, Castanea-Fagus) (650 cal. yrs. BP-until present)
Pollen of Castanea dominates with 95% in the uppermost samples, accompanied by other tree and herb pollen taxa with rather low values such as Fagus, Pinusdiploxylon-type, Poaceae, Cichoriaceae, Chenopodiaceae, Plantagolanceolata.
Peat bog Belasitsa 1 (site 35)
This small peat bog is located on a north-facing slope above the timber-line at 1640 m (41°20’08.82”N, 23°00’15.18”E) nearby a small spring (Fig. 3). The bog vegetation is composed of Festucanigrescens, Nardusstricta, Deschampsiacespitosa, Eriophorumlatifolium, Juncuseffusus, Ranunculusmontanus, Cirsiumappendiculatum, Calthapalustris, etc. (Panovska et al., 1990).
<italic>Coring, lithology and radiocarbon dating</italic>
A sediment core 90 cm long was obtained with Dachnowsky hand-corer equipment. The lithology of the sediments is: 0-10 см peat, 10-80 см peat with sand, 80-90 см sand. The radiocarbon age of one sample of bulk sediment was determined and the result is shown in Table 27. The age of the bottom part of the core is provisionally estimated at c. 2500 cal. yrs. BP.
<italic>Pollen analysis</italic>
Pollen analysis was performed at 10 cm interval and a percentage pollen diagram is constructed (Fig. 105). On the pollen diagram three local pollen assemblage zones (LPAZs) are delimited (BLa-1 to BLa-3). Brief descriptions are as follows:
31AD8C05-AEA1-5CC1-B0D0-AFEBA073A250
Percentage pollen diagram of Peat bog Belasitsa 1.
https://binary.pensoft.net/fig/1672977
LPAZ BLa-1 (90-67 cm, Fagus-Pinusdiploxylon-Poaceae) (~2500-2000 cal. yrs. BP)
The dominant tree pollen taxa are Fagus 10-20% and Pinusdiploxylon-type 14-18%, accompanied by Quercus, Carpinusorientalis/Ostrya, Alnus and Tilia each with 2-4%. Pollen of Castanea is sporadically found. The herb pollen taxa are represented by Poaceae 12-20%, Rumex 10-20%, Cichoriaceae 8%, Plantagolanceolata up to 20%, Scleranthus 5-7%.
LPAZ BLa-2 (67-25 cm, Fagus-Castanea-Poaceae) (~2000-700 cal. yrs. BP)
The pollen curve of Fagus retains 15-12%, while Pinusdiploxylon-type is below 10%. The pollen curves of Juniperus and Castanea appear each with 1-3%. The other tree taxa demonstrate no changes in their pollen frequencies. The presence of Bruckenthalia pollen with 10-12% is considered a local effect. The participation of Poaceae rises to 30-35%. Pollen of Triticum-type, Rumex, Plantagolanceolata, Ranunculaceae, Cichoriaceae, Fabaceae is determined. Pollen of Cyperaceae reaches 20%.
LPAZ BLa-3 (25-0 cm, Fagus-Poaceae-Castanea) (700 cal. yrs. BP-until present)
The pollen curve of Fagus slightly decreases, accompanied by a rise for Poaceae, Juniperus, Achillea-type, Ranunculaceae, Cyperaceae pollen. No changes are recorded for the participation of Castanea pollen.
11.3 Vegetation history in the Belasitsa Mountain
The information from the pollen diagram of Mire Gyola is rather valuable as it reveals the dynamics in the vegetation cover on the northern slopes of the mountain at low altitudes for the last 8500 years. Of particular interest is the history of Castaneasativa because this is the first long record from Bulgaria which throws light on the ongoing discussion about the spontaneous or anthropogenic origin of sweet chestnut in the country. During the first stage of vegetation development (pollen zone BL-1, Fig. 104) which started more than 8000 years ago, the main tree at the elevation of the study site was sweet chestnut. It was accompanied by Quercus, Carpinusorientalis, Ostryacarpinifolia, Carpinusbetulus, Tilia, some Juglans, Fagus and Alnus on wetter places. This deciduous forest was rather sparse and on drier places with lower soil humidity thrived various herb species from Cichoriaceae, Chenopodiaceae, Brassicaceae, Asteraceae (Artemisia, Cirsium, Achillea). Among them Artemisia dominated over large areas. Pines were distributed at higher altitudes compared to other tree species. For this period archaeobotanical data are lacking to indicate if the Neolithic people in the region had introduced sweet chestnut for cultivation. The palynological evidence confirms that by that time Castaneasativa was spontaneously growing alone or in mixtures with other deciduous trees on the northern slopes of the mountain.
The review of Krebs et al. (2004) presented an attempt to develop a Castanea refugium probability index on the localization of sweet chestnut refugia in Europe and its subsequent migration through the Holocene based on paleobotanical data (an extended palynological approach and macro-remains). One of the main conclusions was the identification of Southeastern and Southwestern Bulgaria as potential medium-probability refugia territories that required further studies. The main argument for Southwestern Bulgaria was the appearance of a minimal amount of pollen (0.5-1%) after 7500 cal. yrs. BP. The new palynological evidence from Mire Gyola effectively supports this hypothesis and quite probably this area sheltered sweet chestnut in postglacial time.
A later study on this topic, using a palaeodistribution modelling approach on a European scale for two crucial periods, i.e. Last Glacial Maximum and mid Holocene (Roces-Díaz et al., 2018), detected for the LGM potential refugia on the three large Mediterranean peninsulas (Balkan, Italian and Iberian), along the Atlantic coast of France and Spain, and along the southern coast of the Black Sea. This distribution was validated by fossil records, and is also in agreement with genetic analyses of the species. The results also suggest a postglacial expansion of Castaneasativa in the mid-Holocene, when climate conditions were more favorable for it than current climate conditions in Europe. So that, some of the isolated populations in Southern Central Europe and on the Mediterranean peninsulas could represent current refugia from the Holocene expansion. However, the later influence of humans also has to be considered.
A similar conclusion can also be assumed for the distribution of Juglans. Walnut is considered as a native tree species to some regions of Bulgaria, like in the northwestern montane part of the country, where this tree grows on rocky, sandy terrains, far away from the villages (Velchev, 1971). The nearest to Belasitsa Mountain palynological site studied is the Peat bog in the Maleshevska Moutain located above the present timber-line. On the relevant pollen diagram, the appearance of Castanea and Juglans is synchronous c. 4800 cal. yrs. BP (Fig. 99) or 3500 years later compared to the pollen diagram from Mire Gyola, which presumes also anthropogenic influence. This result corresponds well to the existence of Early Bronze age settlements in the valley of the Struma river (Marinova et al., 2012).
The beginning of the next stage of dynamic changes in the forest cover of the Belasitsa Mountain (pollen zone BL-2, Fig. 104), following the radiocarbon chronology, can be defined at c. 5000 cal. yrs. BP. First of all, it was characterized by a sharp reduction of the areas occupied by Artemisia and some of the other herbs. The participation of Castanea, Pinus, Alnus, and Tilia increased and the presence of Abies was also recorded. These changes suggest a rise in air and soil humidity which had a favorable effect on the spread and enlargement of the forest cover. Subsequently, during the time of the Roman rule (pollen zone BL-3, Fig. 104), the cultivation of sweet chestnut was widely practiced as its valuable fruits and timber were used for various purposes. On the pollen diagram the participation of plants considered as indicators for anthropogenic disturbance in the forest cover such as Chenopodiaceae, Polygonumaviculare, Cirsium and Cichoriaceae increases.
The palynological information from Peat bog Belasitsa 1 situated above the present timber-line reveals the vegetation dynamics at higher altitudes over the last c. 2500 years (Fig. 105). Low quantities of Castanea pollen, evidently air-transported upslope, are present in the fossil record. After II-nd-III-rd cent. AD the participation of Castanea pollen increased, which can be explained by the intensification of the agricultural activity of the local people. By that time, at high altitudes, on the place of the deforested coniferous and partly beech forests, spread groups of Juniperus and various herbs (pollen zone BLa-2, Fig. 105). Quite probably, the enlargement of the forest vegetation at 400-800 m on the northern slopes of the mountain, dominated nowadays by communities of Castaneasativa, started in historical time. As found for Northern Greece, the spread of Juglans, Castanea and Platanus was associated with human economic activity since 1200 yrs. BC, and especially during the Roman rule in these lands (Bottema, 1980, 2000).
The final stage of the forest development spans the last 5-6 centuries (pollen zone BL-4, Fig. 104). It was characterized by the widespread of Castaneasativa and a slight increase for Fagus communities. Pines, most probably Pinussylvestris, declined considerably while the presence of Carpinusorientalis and Corylus indicated periodical openings of the forest canopy. Beyond doubt, this was the time of the strongest anthropogenic impact on the natural forest cover in the mountain.
More detailed palynological and paleoecological information on the changes in the vegetation cover after 650 cal. yrs. BP (XIV-th cent. AD) on the southern slopes of Belasitsa Mountain is presented by Athanasidis et al. (2003). To a large extent, this information can also be accepted for the northern slopes. Between 650 and 450 cal. yrs. BP the tree vegetation was already severely restricted in its distribution. Above 1400 m fragments of Pinus communities were still found, while Fagus and Abies were represented by separate stands. From 460 to 260 cal. yrs. BP (XVI-th-XVIII-th cent. AD) as a result of increasing human intervention, much of the communities of Pinus were destroyed, with a subsequent lowering of the timber-line. In the course of the above time interval there was a short-term expansion of the areas occupied by Fagus, which can be explained by both human activity and the climate conditions during the Little Ice Age. A similar late maximum in the spread of Fagus was also established for several Greek mountains bordering with the Republic of North Macedonia (Gerasimidis, Athanasiadis, 1995). Subsequently, a profound decline in the distribution of the forest vegetation was recorded as anthropogenic interventions took place in all vegetation belts and deforested areas were colonized by herb vegetation. Regarding Castaneasativa, which grows nowadays in the northeastern Greek part of the Belasitsa Mountain, this tree started slightly to enlarge its area as the oak forests declined (Athanasiadis et al., 2003).
12. ANTHROPOGENIC IMPACT ON THE NATURAL VEGETATION
The natural vegetation of Bulgaria was significantly influenced by the millennial diverse human activity. One of the important issues in considering the impact of Man in the past on the vegetation is related to the introduction of agriculture, the practice of animal husbandry and the acquisition of plant material for various purposes. In Southwestern Bulgaria this impact started c. 8000 years ago. A basic role in the establishment of the nature of this activity and the degree of anthropopression is attributed to paleobotanical research, including the study of plant remains from archaeological sites, or plant material used for radiocarbon dating, and especially to pollen analysis to infer the past vegetation cover. Pollen analysis is also one of the powerful tools to reconstruct climate changes and thus presents crucial evidence on the impact of climate on human cultures.
The palynological archives provide information on the livelihood of the people during the different historical epochs on regional scale. The comparison of these data with paleoethnobotanical evidence from archaeological sites presents a reliable picture of the land management but also of the anthropogenic impact on the natural vegetation. Pollen grains from cultivated cereals such as Cerealia-type, Triticum-type, Hordeum-type, Avena-type and Secale can be considered as “primary anthropogenic indicators” for agricultural activity. Their appearance in the pollen diagrams is an indication for cereal crop cultivation in the landscape, accordingly, in the qualitative and quantitative composition of the flora in general. Another group of pollen taxa which reflect a long-lasting presence of human impact like ruderalization and animal husbandry on the landscape are specific for a given area and considered as “secondary anthropogenic indicators” (Behre, 1981; Faegri, Iversen, 1989).
The methodological approach for the selection of pollen taxa as anthropogenic indicators from pollen diagrams for Central Europe, the Mediterranean and Greece, in the assessment of human activity has been discussed in detail (Behre, 1981, 1988; Bottema, 1982; Bottema, Woldring, 1990; Brun 2011). To a large extent, the views of the above authors on “primary” and “secondary” anthropogenic indicators can be accepted for pollen diagrams from Bulgaria (Marinova et al., 2012). For our study region, a specific group of “secondary indicators” was defined (Plantagolanceolata, Rumex, Scleranthus, Urtica, Polygonumaviculare, Juniperus) (Bozilova, Tonkov, 1990). Quite often, considering the overall anthropogenic signals in the pollen assemblages, also pollen from Poaceae, Artemisia, Chenopodiaceae, and Cichoriaceae can be included in this group, indicating opening of the woody vegetation by humans (Bottema, Woldring, 1990). Even Iversen (1947) pointed out that a sharp change in the tree/herb pollen ratio in favor of herb taxa can be considered as an indication of anthropogenic interference with natural vegetation. On the other hand, such a change in this ratio can also be caused by climate change especially in the first half of the Holocene.
The anthropogenic changes in vegetation can also be correlated with the charred particles that occur together with pollen grains in the sediments. The increased concentration of charcoal particles is considered evidence of natural or Man-made fires. The absolute number of microcharcoal particles counted on pollen slides is commonly used by paleoecologists to study the occurrence of past fires and their effects on the ecosystems (Tinner, Hu, 2003). The relationship between the number of charred particles and the frequency of fires is complex, but it can be assumed that the latter is in general connected to the maxima of charred particles and fragments of subfossil wood in sediments (Tolonen, 1986).
The available archaeological information for a given study area is essential in interpreting the palynological data of the anthropogenic impact on vegetation. The territory of Southwestern Bulgaria is of special interest for studies on this topic as its natural vegetation has been influenced by anthropogenic activity since at least 8000 years ago, starting with the introduction of Neolithic farming and continuously increasing through millennia of human occupation.
The development of the praehistorical cultures in Southwestern Bulgaria, and particularly along the Struma river valley, is a key question in Balkan praehistory. The direct territorial connection of this region with the northern Aegean coast, and from there with Anatolia, has influenced the specific dynamics of cultural changes through all praehistoric periods (Pernicheva, 1995; Nikolov, 2007). According to archaeological research, the neolithization in Southwestern Bulgaria is an early phenomenon (Todorova et al., 2007) and it delineates the boundary between hunter-gatherer societies and the more developed societies of early farmers and pastoralists. An important aspect of the Neolithic was the cultivation of plants and breeding of animals, which in turn caused lasting and significant changes in the surrounding vegetation.
The transition from appropriating to productive economy took place outside Europe, on the territory of the "fertile crescent“ - Palestine, Zagros, Mesopotamia (Zohary et al., 2012). At the end of the 8-th millennium BC the Neolithic was already fully developed as the beginning of the cultivation of cereals by selection from the wild growing ones in the region has begun between 10500 and 9250 14C yrs. BP (Tanno, Willcox, 2006). In the second half of the 7-th millennium BC part of the agricultural settlements were established on the Balkan peninsula.
The territory of Southwestern Bulgaria is considered also as one of the primary routes for the neolithization of Southeastern Europe, the Balkan peninsula in particular (Lichardus-Itten et al., 2006), which according to the available archaeological evidence and radiocarbon dates started around 6200/6100 cal. BC (Görsdorf, Bojadziev, 1996; Bojadziev, 2009). In this sense the valley of the Struma river has served as a connecting link between Aegean Thrace and Central Europe. Along its length and north along the Iskar river, the main central European communication artery, the Danube river, was reached. At the end of the 7-th and the beginning of the 6-th millennium BC this was one of the main routes along which agriculture and animal husbandry from Anatolia has penetrated in Europe (Todorova et al., 2007; Krauß et al., 2018).
The rapid spread of the neolithic culture and agriculture to Southeastern Europe can be viewed as a direct response to the abrupt climate change around 8200 cal. yrs. BP (6200 cal. BC), which led to important, irreversible and rapid changes in the then socio-economic and religious life of the population in significant areas of Western Asia and the Balkans. It should be noted that a number of important archaeological settlements either arose (Northwestern Anatolia, Greece, Bulgaria) or were abandoned (Cyprus). This abrupt climate fluctuation is thought to have caused a drought in the western parts of the Eastern Mediterranean, forcing the early farmers to move from Anatolia to Macedonia and the fertile plains of Thessaly, as well as to Southwestern Bulgaria (Weninger et al., 2006, 2009).
The emergence of Early Neolithic settlements in the valley of the Struma river occurred, according to the available absolute dates, about 300 years before the Karanovo-I culture in Thrace which was among the oldest in Europe. These settlements were situated in the foothills of the mountains, between 400 and 650 m (Kovačevo, Topolnitsa, Brezhani, Ilindentsi, Bulgarčevo, Mursalevo, Kremenik, Galabnik, etc.) (Fig. 106) and, quite probably, their location reflected favorable climate and ecological conditions (Todorova, Vaisov, 1989; Ivanova et al., 2018). They showed in a new light the social structure, livelihood and cult sphere of praehistoric Man not only in the region but also in Southeastern Europe as a whole.
18BA1F2F-7D75-5763-A428-6931731A5A3D
Map of praehistorical settlements in Southwestern Bulgaria (Neolithic-Bronze epochs) with paleoethnobotanical remains listed in Table 28 (modified after Tonkov, 2021).
https://binary.pensoft.net/fig/1672978
During the second half of the Early Neolithic and during the Late Neolithic, large settlements appeared, located in the valley itself. At the end of the Late Neolithic and the beginning of the Early Eneolithic the settlements moved to naturally protected places (Grebska-Kulow, Kulow, 2007). After this period, the number of the settlements decreased significantly and this trend continued during the Early Bronze Age.
Information about the Early Eneolithic (4750-4600 yrs. BC) is provided by the excavations in Slatino (Chohadziev, 2006) after which the number of settlements along the Struma river decreased during the Late Eneolithic.
Materials relatеd to the Early Bronze Age (3200-2000 cal. BC) were found along the Blatna river, Radomir district (Alexandrov, 1994) and at the site Kovačevo (Lichardus-Itten et al., 2002). The Late Bronze Age (1600-1200 cal. BC) is documented in several places along the middle and lower course of the Struma river and archaeological sites of special importance are Kamenska čuka, Krasto and Marikostinovo. By that time, a second maximum was registered in terms of the number of settlements and human activity (Grebska-Kulowa, Kulow, 2007). Of great importance for the reconstruction of the praehistorical settlement history of the Struma region is the significant decrease of settlement activity established (Todorova et al., 2007). Between the Early Bronze Age and the beginning of the Late Bronze Age there is a chronological hiatus of c. 600 years from which no particular sites and cultural content have yet been found (Bojadziev, 2007).
The paleoecological reconstructions from Southwestern Bulgaria were used for inferring the human impact on the vegetation and landscape during the last 8 millennia. They are based on data from pollen analyses of lakes and peat bogs, plant macrofossils, archaeobotanical finds and radiocarbon dating (Bozilova, Tonkov, 2007). Against the background of the archaeological situation, attention should be paid to some objective facts in the analysis of the presence of the two groups of anthropogenic indicators in the pollen diagrams. First, the investigated palynological sites with a couple of exceptions are located above 1600 m, where the transport of pollen from cultivated cereals is very limited. Second, a significant part of these sites is relatively far from the nearest studied praehistorical settlements. Third, the time span covered and the chronological resolution of the pollen cores are variable, which sometimes makes it impossible to assess the anthropogenic impact from palynological data for earlier archaeological periods.
Pollen from primary (Cerealia-type, Triticum-type, Hordeum-type, Secale) and secondary (Plantagolanceolata, Rumex, Scleranthus, Urtica, Polygonumaviculare, Juniperus) anthropogenic indicators, confirming the economic activity of the local population, is present after 10000 cal. yrs. BP (8000 cal. BC) in the diagrams from Southwestern Bulgaria. There are two distinct periods in the presence of these indicators in the region. The first one from 10000/9300 to 6500/5600 cal. yrs. BP (8000/7300 to 4500/3600 cal. BC) is characterized by their sporadic presence. During the second period, which started after 4300/4000 cal. yrs. BP (2300/2000 cal. BC), the participation of anthropogenic pollen indicators is constant and significant (Fig. 107).
68743BFE-167E-59E5-891B-14BFAAF38128
Summary scheme for the presence of anthropogenic indicators in the pollen diagrams from Southwestern Bulgaria (modified after Tonkov, 2021).
https://binary.pensoft.net/fig/1672979
During the first period single pollen grains from Secale were determined in the Core-2 from Lake Suho Ezero (Southwestern Rila Mountain) (Fig. 42) which are considered to belong to the wild perennial species Secalemontanum (Kozuharov ed., 1992). The find of Cerealia-type and Triticum-type pollen c. 6500-5700 cal. yrs. BP (c. 4500-3700 cal. BC) probably reflects agricultural activity during the Eneolithic and the Early Bronze Age. In the diagram Kupena-2 (Western Rhodopes Mountain) pollen of Secale, Hordeum-type and Triticum-type appeared already at the begining of the Holocene, originating also from wild-growing species and not linked with human activity. (Fig. 70).
The radical change in the quantitative share of the anthropogenic pollen indicators started in the second period after a gap of 1600-2000 years. The palynological evidence suggests both agriculture at the foothills of the mountains and the use of mountain meadows for seasonal grazing during the Late Bronze Age. The intensification of the anthropogenic activity coincides with the permanent establishment of Fagus and Piceaabies in the Rila and Northern Pirin mountains, which supports the assumption that Man has helped the spread of these tree species by felling and fires (Feurdean et al., 2019).
In most of the studied sites during the second period a continuous occurrence and increase is observed for both groups of anthropogenic pollen indicators and microcharcoal as well. Pollen diagrams from different parts of the Rila Mountain revealed the steady presence of Cerealia-type pollen after c. 4000 cal. yrs. BP (2000 cal. BC), of Secale, Triticum-type and Hordeum-type pollen after 3000/2200 cal. yrs. BP (1000-200 cal. BC), alongside with a continuous presence of Plantagolanceolata pollen after c. 4500/4000 cal. yrs. BP (2500-2000 cal. BC). Numerous fragments of charcoal found just before 3770 cal. yrs. BP and c. 2800 cal. yrs. BP in the sediments of Lakes Ostrezki, Central Rila Mountain, (Figs 34 and 35) point that some of the forest fires were caused by the local population to clear areas for high-mountain seasonal grazing. The next increase in the presence of the anthropogenic pollen indicators began after 2600 cal. yrs. BP (600 cal. BC). Their participation in the pollen diagrams is almost uninterrupted with some site-specific features. The low number of macrofossils of Pinussylvestris and Pinuspeuce recorded after c. 2200 cal. yrs. BP (200 cal. BC) can be explained by the opening of the woody vegetation and the lowering of the timber-line. The abundance of herb pollen taxa, some of them pasture and ruderal plants, and fragments of charred wood in the sediments of Lake Panichishte, Northwestern Rila Mountain, shows that areas around the lake were burned and used for seasonal grazing since the Roman rule (Figs 19 and 21).
From more recent historical times as a convincing example illustrating the diverse human activity is the pollen diagram of Lake Suho Ezero-RM above the Rila Monastery. A general increase of the anthropogenic indicators is observed, such as Plantagolanceolata, Rumex, Sleranthus, alongside with the presence of pollen from cultivated cereals (Cerealia-type, Triticum-type, Secale) (Fig. 39). Historical data on the economy in the valley of the Rilska river (cattle breeding, seasonal grazing, agriculture, timber use, etc.) after the foundation of the monastery in the 10-th century AD (Koeva, 1989) is successfully correlated with the palynological information.
In the area around Mire Kupena, Western Rhodopes Mountain, the human influence at first was restricted to the use of open areas as pastures shown by pollen of Rumex and Plantagolanceolata. Pollen grains of Triticum-type and other cereals were indicative of agriculture at a lower altitude. During the Bronze Age agriculture gained in importance as seen from the comparatively high values for Hordeum-type, Triticum-type pollen, and continued during the Iron Age (Figs 69, 70 and 71). Human presence and activities in the interior parts of the mountain, where the Peat bog Beliya Kanton is located, are indicated by the continuous find of Hordeum-type and Plantagolanceolata pollen (Fig. 75). The fragments of charred wood testify to tree felling and fire clearances on flat ground in order to obtain pastures for cattle-breeding (Fig. 76).
The pollen diagram from Lake Blatisto, Western Rhodopes Mountain, features in detail several cultural phases, interrupted by abandonment of the arable land and partial forest regeneration over the last 2000 years. The presence of Secale and Cerealia-type pollen, accompanied by Rumex, Plantago and Urtica is clearly documented between 400 AD and 590 AD, and since 1600 AD until present, joined by Triticum-type pollen (Fig. 78).
The beginning of the expansion of Piceaabies in the Northern Pirin Mountain coincides with the appearance of pollen from cultivated cereals (Cerealia-type, Triticum-type, Secale) and Scleranthusc. 3000/2500 cal. yrs. BP (1000/500 cal. BC) (Figs 56, 60 and 61). In the area of Peat bog Popovi Livadi, Southern Pirin Mountain, a period of increased anthropogenic impact on the surrounding vegetation is registered between 2530-1300 cal. yrs. BP (530 cal. BC-700 cal. AD). The coniferous and deciduous forests were destroyed on large areas, alongside with the practice of intensive mountain pasture (Fig. 66).
The appearance and subsequent continuous presence of anthropogenic pollen indicators such as Secale, Triticum-type, Rumex, Xanthium-type, Plantagolanceolata in the pollen diagram from the Peat bog Kapaklivets-Platoto on the Vitosha Mountain is recorded since 2300 cal. yrs. BP (300 cal. BC) (Fig. 81).
In the pollen diagrams from Osogovo Mountain the first indication of human presence is recorded between 5000-3500 cal. yrs. BP (3000-1500 cal. BC) when the anthropogenic influence on the vegetation is manifested by finds of Triticum-type, Secale, Plantagolanceolata, Urtica, Rumex pollen (Fig. 96). The high values of Scleranthus pollen found throughout the entire core of Peat bog Osogovo 1 (Fig. 93), with a first peak assigned to the onset of the Late Bronze Age, are of local/extra-local origin pointing to stock-breeding practiced in the nearby vicinity. The intensity of human impact increased notably after 3200 cal. yrs. BP (1200 cal. BC) as documented by a rise of the anthropogenic pollen indicators. The final transformations in the natural forest cover after 2800 cal. yrs. BP (800 cal. BC, the Iron Age) marked the reduction of the coniferous forests and their replacement by beech. These changes in the vegetation cover appear contemporaneous with an increase of the paleofire activities and the subsequent peaks of the anthropogenic indicators point to diversification of human impact (Marinova et al., 2012). In medieval times, after 1230 cal. AD, the impact of humans on the natural woods intensified as demonstrated by the decline of the pollen curves of Pinusdiploxylon-type and Fagus, and the rise of Poaceae, Juniperus, and Plantagolanceolata pollen (Fig. 93). The deforestation led to the enlargement of the areas for summer pasture land and the establishment of the present-day open vegetation cover in the highest parts of the mountain.
Signs of human presence are not recorded from the pollen diagrams of Tschokljovo Marsh, Konyavska Mountain, between 9000 and 7200 cal. yrs. BP (7000 and 5200 cal. BC). By that time the mountain slopes were covered by mixed oak forests with Tilia, Corylus, Ulmus, some Carpinusorientalis/Ostryacarpinifolia, Carpinusbetulus, and above them occurred stands of Pinus and Abies. For the the following time interval of c. 3000 years (7200-4000 cal. yrs. BP or 5200-2000 cal. BC) the most interesting feature, however, was the continuous presence of Juglans pollen, probably indicating its native distribution in this area rather than cultivation by the local population. Until the start of the Roman rule when pollen of Cerealia-type, Plantagolanceolata, Centaureacyanusappears in the fossil record (Fig. 91) the indications of human presence and activity in the area were sporadic.
In the pollen diagram from the Maleshevska Mountain three distinct periods of human impact can be recognized (Fig. 99). During the earliest period 7500-4760 cal. yrs. BP (5500-2760 cal. BC, Middle/Late Neolithic-Early Bronze Age) when coniferous forests were widely distributed and below them mixed oak forests developed, the presence of Cerealia-type pollen in the last quarter of the 6-th millennium BC might reflect settlement activity and cereal cultivation in the valley of the Struma river. In the course of the next period 4760-2800 cal. yrs. BP (2760-800 cal. BC, Early Bronze Age-Early Iron Age) when a sharp decline in the areas occupied by Abies forests is observed, the uninterrupted presence of the anthropogenic pollen indicators (Cerealia-type, Plantagolanceolata, Rumex, Scleranthus) clearly points to the practice of agriculture in the foothills of the mountain and extended sheep/goat and cattle-breeding in the lower mountain areas. The last period which started c. 2800 cal. yrs. BP (c. 800 cal. BC) is characterized by a strong anthropogenic influence on the vegetation. At lower elevations the oak forests were disturbed and replaced by secondary communities dominated by Carpinusorientalis and Quercuspubescens, while at higher elevations the beech forests replaced the conifers (Marinova et al., 2012). The significant increase and presence of anthropogenic pollen indicators such as Triticum-type, Secale, Cerealia-type, Plantagolanceolata, Rumex, Cichoriaceae, Urtica, Scleranthus, as well as the decline of almost all tree species, was a consequence of the permanent settlement in these lands.
For the northern slopes of the Belasitsa Mountain the most significant change in the vegetation cover caused by the anthropogenic intervention started in historical times, after c. 2000 cal. yrs. BP, with the widespread cultivation of Castanea for its valuable fruits and timber, synchronously with that of Platanus and Juglans. Pollen grains from Triticum-type and the presence of secondary anthropogenic pollen indicators (Plantagolanceolata, Scleranthus, Cichoriaceae) are associated with human economic activities, especially during the Roman rule (Fig. 105).
The palynological information from Southwestern Bulgaria is convincing in terms of the practice of cattle breeding, mountain agriculture and enlargement of grazing areas through felling or fires, which led to lowering of the upper timber-line. On the other hand, the pollen records provide less information on medieval land use either because of low resolution or insufficient radiocarbon age control for this period.
The palynological data for the anthropogenic impact on the vegetation cover during the Neolithic, Eneolithic and Bronze Age are confirmed also by the paleoethnobotanical finds from praehistorical settlements in Southwestern Bulgaria (Chakalova, Bozilova, 2002; Marinova, 2006; Marinova et al., 2002, 2012, 2016, 2017; Popova, 2003, 2009; Popova, Marinova, 2007; Marinova, Thiebault, 2008; Marinova, Valamoti, 2014; Marinova, Ntinou, 2018; Marinova, pers. commun., etc.) (Fig. 106; Table 28).
Paleoethnobotanical materials from praehistorical settlements in Southwestern Bulgaria (Neolithic-Bronze epochs) (modified after Tonkov, 2021).
The Neolithic agriculture was well developed and relied mainly on Triticummonococcum (einkorn) and Triticumdicoccum (emmer). The wide distribution of Triticummonococcum was due to its adaptability to different environmental conditions. Individual seeds with morphological features which correspond to those of Triticum aestivum/durum were also found. In addition to wheat, barley was also grown in smaller quantities, mainly Hordeumvulgare var. vulgare, but also Hordeumvulgare var. nudum. The single finds of Panicummilliaceum (millet) in the settlement Drenkovo (Kreuz et al., 2005) raise the question of its possible cultivation, but in the view of recent large-scale studies with numerous radiocarbon dates it is suggested that such singe finds in Neolithic layers have intrusive character (Filipovič et al., 2020).
Along with cereals, there were various accompanying weed species such as Bromus sp., Polygonumaviculare, Setariaviridis, Phleumphleoides, Galium sp., Verbenaofficinalis, Centaurea sp., etc. Legumes were second in importance, mainly Lensculinaris, Lathyrussativus and Viciaervilia. Of interest are the finds of Cicerarietinum. The plant is part of the Near Eastern crop assemblage (Tanno, Willcox, 2006a) but almost unknown so far according to paleobotanical data outside Levant and Anatolia. Its presence in these settlements proves that it came together with the whole Anatolian complex of cultivated plants on the territory of the country (Marinova, Popova, 2008).
The determination of plant remains in storages from the Early Neolithic site Slatina in the capital Sofia, covering several occupation levels from c. 6100 until 5650 BC, revealed their significance for the food economy and diet of the ancient inhabitants. The dominant annual crops were einkorn and emmer, usually in proportion 2:1, comprising over half of all stored annual crops and c. 70% of all cereals. A minor component of little importance was “new glume wheat”– possibly Triticumthimopheevii. Barley was of minor significance considering its quantity, while lentil (Lensculinaris) reached nearly 25-20% of all stored crops. The majority of charred remains from gathered fruits (seeds of Pyrus/Malus, fruit stones of Prunuscerasifera and Cornusmas) were not found in storage vessels, probably being stored in some perishable containers (Marinova, pers. commun.).
In the cultural layers of the Neolithic settlement mound near Rakitovo, Western Rhodopes Mountain, a large quantity of charred cereals was established from Triticummonococcum, Triticumdicoccum, Hordeumvulgare and Hordeumvulgare var. nudum, and from Bromus sp. These finds confirm that ancient agriculture was well developed in this part of the mountain. Einkorn was probably grown as monocultivar on a small area while emmer was cultivated together with other cereals. The most important crop was Hordeumvulgare followed by Triticumdicoccum. Vegetative remains such as stems and leaves, chaff and straw from cereals were also determined (Chakalova, Bozilova, 2002).
For the subsequent Eneolithic period the archaeobotanical evidence suggests certain continuity of the crop spectra with some dominance of einkorn and emmer. However, it seems that in the spectrum of leguminous crops most important was the drought resistant Viciaervilia established from the settlement Galabnik (Marinova et al., 2002). Of interest is also to mention that at this site a storage find of Chenopodium seeds was recoverd pointing also to use of wild plant ressouces (famine food?) probably from wetlands in the surroundings.
The finds of charred or mineralized wood in archaeological sites is of particular interest for paleobotanical research because they are usually associated with its use for various purposes – primary firewood but also as building material, tools, etc. It was almost always collected from the surrounding area and thus provided valuable information about the woody flora.
Most of the praehistorical settlements in Southwestern Bulgaria were located at relatively low altitudes (300-800 m) and the analysis of wood from their cultural layers complemented the knowledge about the vegetation at the foothills of the mountains. These studies provide direct information on the use of wood in the settlements and clarify the importance of the lower mountain belt as a valuable source of plant material for various purposes, including leaf fodder.
In the materials from the Neolithic settlements Galabnik (Marinova et al., 2002), Rakitovo (Chakalova, Bozilova, 2002), Kovačevo (Marinova, Thiebault, 2008), Topolnitsa (Popova, 2009), Balgarčevo (Marinova, 2017), Ilindentsi (Marinova, Ntinou, 2018) wood of Quercus predominates, which is a confirmation of the widespread distribution of oak forests in the lower mountain belt during the climatic optimum of the Holocene. There are also numerous fragments of wood from Rosaceae (Pomoideae, Prunoideae), followed by those of Cornusmas, Corylus, Acer, Ulmus, Fraxinus, Pinus sp. This is a general tendency of the Neolithic woodland use observed for the broader study region (Marinova, Ntinou, 2018). The paleobotanical material from Rakitovo is rich in charred wood of Quercus, followed by Pinus sp., Piceaabies, Abiesalba, Ulmus, Corylus, Viburnum, Fraxinus. The age of this settlement mound located in the Western Rhodopes Mountain at 800 m coincides with the Holocene climatic optimum when the increased air and soil humidity favored the wide distribution of mixed oak forests and the gradual spread of the conifers also to lower altitudes (Chakalova, Bozilova, 2002).
The find of wood from Fagus in Galabnik is especially important, as according to palynological data the presence of beech in the vegetation of Southwestern Bulgaria c. 8000-7500 cal. yrs. BP (6000-5500 cal. BC) was sporadic. Fragments of wood from Salix, Populus and Alnus prove that these species were an integral part of the riparian plant communities and were used by humans. The origin of wood from Buxus in the Neolithic layers remains unclear (Marinova et al., 2002).
Abundant archaeozoological and scarce botanical materials were found in the cultural layers of final Early Neolithic to Early Bronze Аgе in the praehistorical settlement Vaxevo located at 600 m on the southeastern foothills of the Osogovo Mountain. The bones from cattle, sheep, goats and pigs suggest that stock-breeding was a significant part of the human economy (Chohadziev et al., 2001). The evidence of agriculture from this site shows several storages of cultivated cereals dominated by Hordeumvulgare and Triticummonococcum. The Thracian and Roman periods of occupation witnessed further development of agriculture, vine-growing, stock-breeding and ore-mining. The forests served as an important source for wood used for construction purposes, heating and metallurgy. The local economy flourished as the Romans introduced advanced methods for the cultivation of the fields (Bozilova et al., 1994).
The wood from the Late Bronze age settlements Kamenska čuka (Popova, 1998) and Koprivlen (Popova, Marinova, 2007) has almost the same composition and the finds from Abies, Pinussylvestris, Juniperus deserve attention in support of the palynological data on the distribution of coniferous forests of Abies and Pinus in the western border mountains during the mid-Holocene.
With the introduction of iron and the growing demand for timber many local tribes moved to montane areas. This resettlement is established in the pollen diagrams from the Osogovo-Belasitsa mountain range c. 3000 cal. yrs. BP (1000 cal. BC), when the oak forests were disturbed and the coniferous woods were gradually replaced by beech forests.
The changes in the landscape during the Roman rule and the Medieval period reflect regional environmental features and were forced by the diversification of the anthropogenic activity. The paleoethnobotanical materials from the Iron Age, the Antiquity and the Middle Ages for Southwestern Bulgaria are very scarce against the background of the abundant archaeological information. In this aspect of interest are the crop (Triticum aestivum/durum, Triticummonococcum, Triticumdicoccum, Hordeumvulgare, Panicummilliaceum, Secalecereale, Avenasativa, Lensculinaris, Pisumsativum, Viciaervilia, Vitisvinifera) and wood charcoal assemblages (Abies, Pinussylvestris, Quercus sp., Fagus, Corylus, Fraxinus) found in the settlement Koprivlen dated predominantly to the Late Iron Age (Popova, 2003).
13. CONCLUSION
The paleobotanical and paleoecological research on the postglacial vegetation history in Southwestern Bulgaria with the application of several research approaches allows the presentation of some general issues and summaries. They are based on the trends and patterns in the development of vegetation, climate changes, anthropogenic impact and some specific regional features as well. The scientific results expand the available knowledge on this region as an integral part of the country and the Balkan peninsula in terms of unravelling past environmental changes.
The reconstruction of the vegetation cover in the study area extends back to c. 30000 cal. yrs. BP (Middle Pleniglacial) in the non-glaciated Western Rhodopes Mountain. The oldest palynological record was obtained from the Mire Kupena. It revealed that by that time the surrounding area was occupied by wooded steppe composed of Pinus sp., Pinuspeuce, stands of Betula, shrubland of Juniperus-Ephedra on dry sandy places, and cold-tolerant herb vegetation dominated by Artemisia, Chenopodiaceae, Poaceae, Apiaceae species. At lower altitudes, under more favorable microclimatic and edaphic conditions, thrived groups of deciduous (Quercus, Carpinus, Tilia, Ulmus, Corylus, Alnus, Fagus) and coniferous (Abies, Piceaabies) trees. This large variety of trees and shrubs affirms the hypothesis that this part of the mountain could have served as one of the Middle Pleniglacial refugial places on the Balkans. Gradually, the pine forest started to expand at the expense of the herbs and over the course of several millennia until c. 24000 cal. yrs. BP the tree vegetation constituted an important part of the plant cover. This vegetation pattern can be compared in broad lines with the results from the upper parts of the long pollen cores with detailed radiocarbon dating collected from the site Tenaghi Philippon in Northern Greece. The time interval 30850-24000 cal. yrs. BP was characterized by the dominance of open Artemisia-Chenopodiceae steppe vegetation with some enlargement of Pinus, accompanied by Quercus and Juniperus during the interstadials, most likely facilitated by short-term increases of precipitation (Wijmstra, 1969; Müller et al., 2011).
The time window 24000-18000 cal. yrs. BP encompassing also the Last Glacial Maximum (23000-19000 cal. yrs. BP) is not presented in the pollen diagrams from Southwestern Bulgaria. A brief look at some pollen records older than 14700 cal. yrs. BP from the northern part of the Balkans in Romania suggests that the landscapes in the Carpathian region during the terminal part of the Pleniglacial were likely covered by open forest mixed with steppe-tundra vegetation. The main tree taxa were of boreal (Piceaabies, Pinus, Juniperus) and cool temperate type (Alnus, Betula, Salix). Scattered deciduous trees (Ulmus, Quercus, Fraxinus, Corylusavellana) were also found. The steppe-tundra assemblages represent a vegetation type that has no analogue to modern vegetation. These consisted of steppic plants composed of herbs growing in open landscape under dry conditions, and tundra elements composed of arctic herbs and shrubs that occurred where the conditions were too cold for trees to grow (Feurdean, Tantau, 2017). In the highest parts of the Carpathians, Rila and Northern Pirin mountains near the glaciers there was probably alpine tundra. Below it, the areas were occupied by open herb vegetation dominated by Artemisia and Chenopodiaceae, along with various species of Poaceae, Asteraceae, Apiaceae, shrubs of Ephedra and Juniperus (Jalut et al., 2005). The presumed microrefugia for different thermophilous tree species such as Quercus, Corylus, Ulmus, Tilia, Carpinusbetulus were located in suitable habitats at altitudes below 1000 m with sufficient moisture, relatively well-developed soils and protected southern exposures (Bennet et al., 1991; Willis et al., 2000). For the mountains of Northwestern Greece and Southern Bulgaria (Western Rhodopes) the presence of pollen from deciduous and coniferous trees/shrubs presumes the existence of refugia at mid-low altitudes (Bottema, 1974; Tzedakis, 2004; Tonkov et al., 2014).
The global climate changes after the Last Glacial Maximum, established simultaneously in ice cores from Greenland and Antarctica, pointed to a trend of gradual climate improvement after 19000 cal. yrs. BP (Blunier, Brook, 2001) in synchronity with the increase in solar insolation in the Northern hemisphere and the onset of melting of ice sheets with subsequent sea level rise (Yokohama et al., 2000). The isotope signal from Greenland manifests a clear warming c. 14700 cal. yrs. BP (Labeyrie et al., 2003) which correlates with a significant retreat and shrinking of the area of the mountain glaciers in the Alps (Husen, 1989).
The assumption for the beginning of significant climate change at the termination of the Late Pleniglacial in Southwestern Bulgaria is reflected in the pollen cores from the glacial lakes in the Rila Mountain. Moreover, the paleobotanical data compared with the deposition of silty clay in the lakes suggest a much earlier retreat of the local circus glaciers above 2300-2400 m (Velchev, 2020) similar to the deglaciation in the Western Pyrenees (Jalut et al., 1992). The gradual enlargement of stands of Pinus, the appearance of Betula and Alnus alongside with increasing July temperatures (Heiri et al., 2014; Tonkov et al., 2022) serves as evidence of climate improvement at the onset of the lateglacial interstadial Bölling/Alleröd. However, the climate at the end of the Pleniglacial and during the Lateglacial remained cold and dry, with temperatures of 5-7°C lower than today. The same trend in the vegetation development is observed in the pollen diagrams from the glacial lakes in the Northern Pirin Mountain (Stefanova et al., 2006; Tonkov, Possnert, 2021).
According to the regional radiocarbon chronology the plant paleosuccession in Southwestern Bulgaria for the last c. 18000-15000 years comprises several well-defined stages. The first stage refers to the termination of the Pleniglacial and the entire Lateglacial, while the rest are related to the Holocene. During the Lateglacial (14700-11600 cal. yrs. BP) in the Rila, the Northern Pirin and the Western Rhodopes mountains open herb vegetation of “mountain-steppe” character dominated by Artemisia-Chenopodiaceae-Poaceae and various cold-resistant and heliophilous species from Achillea, Centaurea, Rumex, Thalictrum, Galium, Dianthus, Brassicaceae, etc. was widely distributed at mid-high altitudes. This vegetation pattern comprised also stands of pines (Pinusmugo, Pinussylvestris, Pinuspeuce), Betula and shrubland of Juniperus-Ephedra, which partly expanded during the interstadial Bölling/Alleröd (14700-12800 cal. yrs. BP). Isolated groups/populations of coniferous (Abies, Piceaabies) and deciduous (Quercus, Fagus, Tilia, Carpinus, Corylus, etc.) trees survived the harsh conditions in sheltered habitats with favorable microclimatic and microedaphic conditions for their growth.
The last pronounced deterioration of the climate during the Lateglacial and return to glacial conditions, the Younger Dryas stadial after 12800 cal. yrs. BP lasted for 1100-1200 years. It was characterized by a readvance of the "mountain-steppe“ herb vegetation with dominants Artemisia, Chenopodiaceae and Poaceae, as well as with retreat of moisture demanding trees to lower altitudes. It should be also noted that the first macroremains of Pinuspeuce and Betula appeared in the fossil assemblages collected at altitudes above 1800 in the Rila and the Northern Pirin mountains.
The next stage in vegetation development for the highest mountains Rila and Northern Pirin was triggered by the rapid amelioration of the climate at the onset of the Holocene when the July temperatures increased with 4-5°C (Tonkov et al., 2022). This led to a significant reduction and retreat of the herb “mountain-steppe” vegetation. The initial afforestation in both mountains lasted for nearly 4000 years from 11600 to c. 8100/7900 cal. yrs. BP and within this stage two phases can be distinguished. During the first one (11600-10200/9900 cal. yrs. BP) pioneer communities of Betula became widespread at altitudes between 1900 and 2200 m on a still poor, skeletal soil cover. These communities were rather sparse and mixed in places with stands of Pinusmugo, Pinussylvestris, Pinuspeuce and Juniperus, which is confirmed by the plant macroremains (needles and stomata) determined. The pollen data present the distribution at lower altitudes of mixed oak forests with considerable participation of Tilia, Ulmus, Fraxinus, Acer. These trees, together with Corylus, reached their maximal development during the second phase after 10200/9900 cal. yrs. BP.
The most significant transformation in the vegetation composition was associated with the Holocene climatic optimum (8000-5000 cal. yrs. BP) when the general trend of warming reached its culmination. The results of physical and chemical analyses of ice cores from Greenland (GRIP, GISP2 and NGRIP) indicated that temperatures were 2-3°C higher than today and the following trend towards cooling after 5000 cal. yrs. BP was gradual (Stuiver et al., 1995; Johnsen et al., 1997; NGRIP Members, 2004). The climatic optimum was preceded by a short-term deterioration of the climate c. 8200 cal. yrs. BP (8.2 ky event) or 7400 C14 yrs. BP, which was the most pronounced cooling during the Holocene in the Northern hemisphere with a duration of 160 years according to data from ice cores in Greenland (Alley, Augustsdottir, 2005). The manifestation of this climatic oscillation on the European continent, including the Balkans, was not one-way. As a direct consequence of it the results from pollen and plant macrofossil analyses in Southwestern Bulgaria after 8000 cal. yrs. BP reflect the widespread distribution of conifers displacing the birch and oak forests.
Also, the spread of the Neolithic culture and agriculture in Southwestern Bulgaria from Anatolia can be considered as a response to the 8.2 ky event, as in this region of the Balkans the ecological conditions have proved favorable for the socio-economic life of the Neolithic settlers (Weninger et al., 2006).
During the climatic optimum (8100/7900-5400/5200 cal. yrs. BP) a coniferous belt was shaped in the Rila and the Northern Pirin mountains composed of Pinussylvestris, Pinuspeuce and Abies in the conditions of general climate change towards cooler summers, milder winters and increased air and soil humidity. The upper timber-line climbed higher than today which was evidenced by the plant macrofossils found. Above the coniferous forest belt on rocky places and on poorer soils Betula retained its pioneering role and the stands of Pinusmugo have become denser. The palynological and macrofossil data from the Osogovo-Belasitsa mountain range (Maleshevska mountain) and the Konyavska Mountain also revealed that after 8000/7000 cal. yrs. BP a vast coniferous belt was shaped dominated by Abies, Pinussylvestris, Pinusnigra and Quercetum-mixed forests below it.
The vegetation cover of the Rila and the Northern Pirin mountains in the first half of the Late Holocene (5400/5200-3000 cal. yrs. BP) was characterized by the final establishment of Fagus and Piceaabies, alongside with the maximal distribution of Pinuspeuce, Pinussylvestris, Pinusmugo, and the commence of Abies decline. During the second half after 3000/2800 cal. yrs. BP in the conditions of more humid and cooler climate the modern vertical distribution of vegetation was established, characterized by the pulsating expansion of spruce, thus reaching its first distribution maximum c. 2800 cal. yrs. BP. In many places Piceaabies shaped the upper timber-line together with Pinuspeuce and Pinus sylvеstris. A significant retreat and reduction were established for the communities of Abies at altitudes between 1400 and 1600 m.
The destructive changes in the vegetation of the Rila and the Pirin mountains were intensified in historical time when areas occupied by Pinussylvestris, Piceaabies, Pinuspeuce and Abies were seriously affected. In many places the upper timber-line was artificially lowered and the new terrains were subsequently occupied by herbs and used for pasture land.
In the Western Rhodopes Mountain the lateglacial interstadial was characterized by the enlargement of Pinus, Pinuspeuce, Juniperus, some Betula and vast spread of Poaceae species. The afforestation in the Early Holocene in the northern part of the mountain started with broad-leaved forests composed of Quercus with Carpinusbetulus, Carpinusorientalis/Ostrya, Ulmus, Tilia, Corylus and minor amounts of Pinus, Betula, Abies. After c. 4700 cal. yrs. BP Fagus began to gain importance chiefly at the expense of the mixed oak communities while in the last 2000 years forests of Pinussylvestris with some Pinuspeuce quickly expanded. In the interland of the mountain forests of Pinus expanded between 11000 and 10000 cal. yrs. BP and afterwards Betula and Quercus firmly established c. 8800 cal. yrs. BP. Low humidity was probably the reason for the persistence of the herb vegetation dominated by Poaceae and less Artemisia and Chenopodiaceae species until c. 9000 cal. yrs. BP. The mixed oak forests started to retreat after 7800 cal yrs. BP, replaced at many places first by Corylus and subsequently by Abies and Fagus, followed by the final establishment and spread of Piceaabies. Spruce was the last tree immigrant in the Western Rhodopes Mountain and began to invade areas particularly in the interior parts, when the shaping of a coniferous belt started (Stefanova et al., 2006; Bozilova et al., 2011).
The development of the vegetation in the Vitosha Mountain during the Holocene over the last 9000 years demonstrates common features on one side with the Rila and Northern Pirin mountains and on the other with the mountains located west from the Struma river. The initial spread of deciduous oak forests with Ulmus, Tilia, Corylus and above them communities of Pinus with stands of Betula, Abies, single trees of Piceaabies and Fagus was followed by an expansion of Corylus after 8400 cal. yrs. BP for nearly 2000 years. An interesting important change is observed in the forest cover between 6500 and 3370 cal. yrs. BP when both Abies and Carpinusbetulus quickly enlarged their areas. Fir has become the main constituent in the dense coniferous forests together with pines. The last c. 3500 years marked the wide distribution of Piceaabies and Fagus as spruce played a dominant role in the coniferous forest belt particularly between 3400 and 2300 cal. yrs. BP with a maximum at c. 2900 cal. yrs. BP. Subsequently, vast areas were deforested at mid-high altitudes between 2300 and 1500 cal. yrs. BP to obtain new pasture land and timber.
In the Osogovo-Belasitsa mountain range and the Konyavska mountain Fagus gradually started to gain importance at the expence of the coniferous woods shaping monodominant or mixed communities with Abies and Carpinusbetulus preferеntially on northern slopes in the transitional zone between the deciduous and coniferous vegetation belts. The distribution of beech on the place of the coniferous woods appeared synchronously in time with that of Piceaabies in the Rila and the Pirin mountains. The widespread of beech was assisted by human activities such as felling of the conifers for timber and other uses, thus resulting in the enlargement of the areas for seasonal grazing on the slopes and the rounded ridges. In the last millennium the deforestation in the Osogovo Mountain has led to the progressive reduction of the remnants of the coniferous communities. In Belasitsa Mountain the most significant change in the vegetation cover on the northern slopes has occurred just before 1760 cal. yrs. BP when the communities of Fagus were seriously affected and the upper timber-line was lowered. As a consequence, the areas occupied by the beech forests were reduced and at lower altitudes an enlargement of Carpinusorientalis, Ostryacarpinifolia, and partly of Quercus and Corylus took place.
The impact of the climate cooling during the Little Ice Age (1550-1850 AD) on the vegetation cover in Southwestern Bulgaria is manifested by the last pulsations of the spruce forests in the Rila and Pirin mountains in the altitudinal range 1600-1400 m mainly on slopes with northern and derivative exposure. According to the palynological evidence, the last expansion of beech in the Osogovo-Belasitsa mountain range about 300 years ago was also favored by this climate change and the local disturbances in the forest ecosystems.
The changes in the natural vegetation cover in the study area were also facilitated by the increasing human activities since the Late Bronze Age such as crop cultivation, animal husbandry, tree felling and fires in order to enlarge pasture land.
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