Ricerc@Sapienza

Mediterranean mid-altitude sites are critical for the survival of plant species allowing for elevationalvegetation shifts in response to high-amplitude climate variability. Pollen records from the southernBalkans have underlined the importance of the region in preserving plant diversity over at least the lasthalf a million years. So far, there are no records of vegetation and climate dynamics from Balkan refugiawith an Early Pleistocene age. Here we present a unique palynological archive from such a refugium, theLake Ohrid basin, recording continuouslyfloristic diversity and vegetation succession under obliquity-paced climate oscillations. Palynological data are complemented by biomarker, diatom, carbonateisotope and sedimentological data to identify the mechanisms controlling shifts in the aquatic andterrestrial ecosystems within the lake and its catchment. The study interval encompasses four completeglacial-interglacial cycles (1365e1165 ka; MIS 43e35). Within thefirst 100 kyr of lake ontogeny, lake sizeand depth increase before the lake system enters a new equilibrium state as observed in a distinct shift inbiotic communities and sediment composition. Several relict tree genera such asCedrus,Tsuga,Carya,andPterocaryaplayed an important role in ecological succession cycles, while total relict abundanceaccounts for up to half of the total arboreal vegetation. The most prominent biome during interglacials iscool mixed evergreen needleleaf and deciduous broadleaf forests, while cool evergreen needleleaf forestsdominate within glacials. A rather forested landscape with a remarkable plant diversity provide uniqueinsights into Early Pleistocene ecosystem resilience and vegetation dynamics.