LATE QUATERNARY CLIMATE AND VEGETATION DYNAMICS IN NORTHEASTERN EURASIA

A sediment core recovered from Dolgoye Ozero, a tundra lake located 10 km north of treeline in northeast Siberia, was analyzed for sub-fossil midge remains, pollen and stomates to investigate late Quaternary climate and vegetation dynamics. Chronological control, based on eight AMS radiocarbon dates, indicates the core spans the latest Pleistocene and Holocene. Notable fluctuations in midge community composition occur during the last 14,000 cal yr BP with the transition from the Pleistocene to the Holocene marked by large shifts in the relative abundances of warm and cold-tolerant midge taxa. The shifts in midge abundance primarily reflect climatic deterioration during the Younger Dryas (YD) stade and climatic amelioration during the early Holocene. An abrupt increase in thermophilous midge taxa immediately prior to the YD is suggestive of rapid warming during the Bølling-Allerød. The Bølling-Allerød was followed by an increase in the relative abundance of cold stenothermic midge taxa during the YD, with a reversion to more thermophilous taxa occurring at the onset of the Holocene. A midge-based inference model for mean July air temperature based on eighty-one lakes with robust performance statistics (R²_jack=0.92, RMSEP=1.00^oC), developed for the pan-Russian Arctic (Self et al. 2011), was applied to the Dolgoye Ozero midge stratigraphy. The results indicate that mean July air temperature was depressed by approximately 2^oC during the Younger Dryas. The midge-based reconstruction also indicates that the Holocene Thermal Maximum in this region occurred between 11,600 and 8000 cal yr BP. Stomates and macrofossils, which record the presence of trees in the area between 8500 and 3500 yrs BP, suggest that the movement of treeline into the area lagged climate amelioration by multiple millennia. The expression of late Quaternary climate variability and environmental change in this region is compared to existing regional records to examine the correspondence of the spatial and temporal patterns of past climate and environmental change in northeastern Eurasia to areas further afield.