Vegetation History In The Lake Ilchir Basin (East Sayan Mountains) For The Last 8500 Years

Holocene climate is more complex both temporally and spatially than is commonly recognized. Pollen records from inland regions are important for understanding past changes in landscapes, assessing the sensitivity of ecosystems to future climatic variations that affect the composition of vegetation and its change over time. High-mountain boreal ecosystems are very vulnerable to climate change, and even minor fluctuations in it can lead to serious natural changes. We carried out analysis of pollen, spores, micro-charcoal particles, conifer stomata, and lithology of an AMS C-14-dated core from high-mountain Lake Ilchir situated in the Eastern Sayan mountains, in order to reveal changes in vegetation and climate since 8490 cal yr BP. The sediments of 133 cm long core consists of gray silty clay and shows no signs of sedimentary hiatuses. Fife bulk sediment samples were dated with an accelerator mass spectrometry (AMS) system.The modern vegetation of the Lake Ilchir basin is ranges from moist forb-grass meadow around the lake to small patches of open larch stands and shrubby birch on the basin slopes.The pollen record presented here is the first continuous and well-dated records from Lake Ilchir covering the last 8490 cal years, allowing detailed reconstruction of vegetation and environmental dynamics in the region.The results of the pollen analysis and pollen-based vegetation and climate reconstruction suggest that grass-dominated meadow communities prevailed in the lake basin from 8490 to 6000 kyr BP. The absence of larch and fir stomata in the sediments suggests the growth of trees rather far from the Lake shore. Probably, the climate in the basin was moderately cold with insufficient moisture. The high Scots pine pollen percentage in comparison with surface pollen spectra suggests a higher than today position of the upper boundary of the pine in response of higher-than-present summer insolation.Between 6000-3700 kyr BP the climate was characterized by warmer than modern winter seasons and high snow cover, which did not allow the soils to freeze and supported the development of fir in the Ilchir Lake basin. However, the increased abundance of larch pollen and stomatal cells of its needles in sediments suggest an increased role of larch in the composition of local vegetation and / or its approach to the lake shoreline. Expansion of the areas of larch means that climate gradually became sharply continental, more arid.The last 3700 years was characterized by a continuing increase in climate continentality and cooling that led to the complete disappearance of fir and appearance of spruce in the lake catchment.The more detailed temporal resolution of future palaeoecological records from this region will improve our understanding of the interaction of the lakes hydrology with climate and will provide valuable information for the efficient use of water resources.