ИСТИНА

The new multi-proxy records of the Holocene environmental and climatic changes in the Western Caucasus revealed from mountainous Lake Khuko (Caucasus State Natural Biospheric Reserve, 1744 m a.s.l.) are presented. Palaeoecological analyses of a sediment core for loss on ignition, pollen, plant macrofossil and macroscopic charcoal allowed us to determine five principal climatic phases with several subphases since 10.5 ka BP. The age model is based on seven AMS 14C dates, supplemented by 210Pb data for the uppermost part of the sediment core. Warm periods (10.5-6.7, 6.7-5.5, 3.5-2.4, 0.8-0.5 ka BP) were characterized by expansion of forests, typical of modern low and middle mountain zones, as indicated by the increase in abundance of Quercus, Ulmus, Corylus and Tilia in the pollen assemblages. Cold periods (5.5-3.5, 2.4-0.8, and 0.5 ka BP-present) are marked by a consistent decrease in organic matter content in lake deposits and possibly higher intensity of the catchment erosion. The changes in pollen assemblages (for instance peaks of Abies, Picea, and Pinus) suggested a potential elevational decline in the boundaries of vegetation belts and expansion of high-altitude woodlands. Abrupt changes in the lake ecosystem were identified between 4.2 and 3.5 ka cal BP marked by a short-term variation in sediment regime and the extremely high concentration of macroscopic charcoal particles, probably caused by intensive fires and climatic fluctuations in the Western Caucasus region during the 4.2 ka event. The study was supported by the Megagant project (agreement No 075-15- 2021-599, 8.06.2021) of the Ministry of Highest Education of Russia.