The possible response of forest ecosystems of south taiga at the south of Valdai Hills on projected future global warming was assessed using analysis of pollen, plant macrofossil and radiocarbon data from four profiles of buried organic sediments of the last interglacial and several cores from modern raised bogs and two small forest mires in the Central Forest State Natural Biosphere Reserve (CFSNBR; Twer region, Russia). The future pattern of climatic conditions for the period up to 2100 was derived using the data of A2, B1 and A1B emission scenarios calculated by the global climatic model ECHAM5-MPIOM (Roeckner E et al 2003 The Atmospheric General Circulation Model ECHAM 5. PART I: Model Description, Report 349 (Hamburg: Max-Planck Institute for Meteorology) p 127). The paleoclimatic reconstructions showed that the optimum of the Holocene (the Late Atlantic period, 4500-4800 14 C yr BP) and the optimal phases of the last interglacial (Mikulino, Eemian, 130 000-115 000 yr BP) can be considered as possible analogs for projected climatic conditions of the middle and the end of the 21st century, respectively. The climate of the CFSNBR during the Holocene climatic optimum was characterized by higher winter (about 3• C higher than at present) and summer temperatures (about 1• C higher than present values). Precipitation was close to present values (about 600-800 mm yr −1 ). Vegetation was represented by mixed coniferous and broad-leaved forest. In the warmest phases of the last interglacial the winter temperature was 5-8• C higher than present values. The summer temperatures were also about 2-4• C higher. Broad-leaved and hornbeam trees were the dominant tree species in vegetation cover.

Modern climate conditions and their possible future changes in the southern part of Valday Hills, Russia, were analyzed using 40-years of meteorological data observations and global model projections. It was shown that the annual, January and July temperatures in the area increased during the last 40 years by about 0.7°, 4.0°C and 0.3°C, respectively. Annual precipitation also increased by about 60 mm. Climate simulations for the period up to 2100 provided by a general circulation model ECHAM5 (MPI Hamburg, Germany) according to B1, A1B and A2 IPCC emission scenarios propose significant changes in meteorological conditions for the study area in the future. The mean annual temperature at the end of the century may rise by 2.2-3.9°C. Increase of January temperatures under different scenarios can range between 3.3 and 6.7°C. Projected increase of annual precipitation can reach 105 mm and it is mainly manifested in growth of winter values.

Effects of possible climatic and vegetation changes on H 2 O and CO 2 fluxes in boreal forest ecosystems of the central part of European Russia were quantified using modeling and experimental data. The future pattern of climatic conditions for the period up to 2100 was derived using the global climatic model ECHAM5 (Roeckner et al 2003 The Atmospheric General Circulation Model ECHAM 5. PART I: Model Description, Report 349 (Hamburg: Max-Planck Institute for Meteorology) p 127) with the A1B emission scenario. The possible trends of future vegetation changes were obtained by reconstructions of vegetation cover and paleoclimatic conditions in the Late Pleistocene and Holocene, as provided from pollen and plant macrofossil analysis of profiles in the Central Forest State Natural Biosphere Reserve (CFSNBR). Applying the method of paleoanalogues demonstrates that increasing the mean annual temperature, even by 1-2 • C, could result in reducing the proportion of spruce in boreal forest stands by up to 40%. Modeling experiments, carried out using a process-based Mixfor-SVAT model, show that the expected future climatic and vegetation changes lead to a significant increase of net ecosystem exchange (NEE) and gross primary productivity (GPP) of the boreal forests. Despite the expected warming and moistening of the climate, the modeling experiments indicate a relatively weak increase of annual evapotranspiration (ET) and even a reduction of transpiration (TR) rates of forest ecosystems compared to present conditions.