Mediterranean mid-altitude sites are critical for the survival of plant species allowing for elevational vegetation shifts in response to high-amplitude climate variability. Pollen records from the southern Balkans have underlined the importance of the region in preserving plant diversity over at least the last half a million years. So far, there are no records of vegetation and climate dynamics from Balkan refugia with an Early Pleistocene age. Here we present a unique palynological archive from such a refugium, the Lake Ohrid basin, recording continuously floristic diversity and vegetation succession under obliquity-paced climate oscillations. Palynological data are complemented by biomarker, diatom, carbonate isotope and sedimentological data to identify the mechanisms controlling shifts in the aquatic and terrestrial ecosystems within the lake and its catchment. The study interval encompasses four complete glacial-interglacial cycles (1365–1165 ka; MIS 43–35). Within the first 100 kyr of lake ontogeny, lake size and depth increase before the lake system enters a new equilibrium state as observed in a distinct shift in biotic communities and sediment composition. Several relict tree genera such as Cedrus, Tsuga, Carya, and Pterocarya played an important role in ecological succession cycles, while total relict abundance accounts for up to half of the total arboreal vegetation. The most prominent biome during interglacials is cool mixed evergreen needleleaf and deciduous broadleaf forests, while cool evergreen needleleaf forests dominate within glacials. A rather forested landscape with a remarkable plant diversity provide unique insights into Early Pleistocene ecosystem resilience and vegetation dynamics.
Bibliographical noteFunding Information:
The SCOPSCO Lake Ohrid drilling campaign was funded by the ICDP , the German Ministry of Higher Education and Research , the German Research Foundation , the University of Cologne (Germany) , the British Geological Survey (United Kingdom) , the INGV and CNR (Italy), and the governments of the republics of North Macedonia and Albania . Logistic support was provided by the Hydrobiological Institute in Ohrid. Drilling was carried out by Drilling, Observation and Sampling of the Earth’s Continental Crust (DOSECC) and using the Deep Lake Drilling System (DLDS). We thank K. Schittek for insightful comments on previous manuscript versions, and N. Mantke and D. Klinghardt for lab work coordination. Palynological processing was performed with the assistance of K. Knoedgen, S. Kyrikou, N. Mai, and L. Swawatzki. K. Panagiotopoulos acknowledges funding from the German Research Foundation (DFG grant PA 2664/2-1 ). We would like to thank two anonymous reviewers for their comments that helped improve this manuscript.
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