Energy and Mass Exchange and the Productivity of Main Siberian Ecosystems (from Eddy Covariance Measurements). 2. Carbon Exchange and Productivity

Direct measurements of CO2 fluxes by the eddy covariance method have demonstrated that the examined middle-taiga pine forest, raised bog, true steppe, and southern tundra along the Yenisei meridian (similar to 90 degrees E) are carbon sinks of different capacities according to annual output. The tundra acts as a carbon sink starting from June; forest and bog, from May; and steppe, from the end of April. In transitional seasons and winter, the ecosystems are a weak source of carbon; this commences from September in the tundra, from October in the forest and bog, and from November in the steppe. The photosynthetic productivity of forest and steppe ecosystems, amounting to 480-530 g C/(m(2) year), exceeds by 2-2.5 times that of bogs and tundras, 200-220 g C/(m(2) year). The relationships between the heat balance structure and CO2 exchange are shown. Possible feedback of carbon exchange between the ecosystems and atmosphere as a result of climate warming in the region are assessed.