The carbon flux in grassland ecosystems of different bioclimatic zones within the Transbaikal region has been studied. The extra-arid steppe (Selenginskoye middle mountain area: sedge-grass-herbage community on meadow-chestnut soil), moderately arid forest-steppe (the Selenga River delta: herbage-grassy community on meadow-subsaline soil), cryoarid forest-steppe (Vitimskoye plateau: grass-herbage community on meadowchernozem cryosoils) were among them. NPP values in all ecosystems were low: 2404 g/m2 per year in the forest-steppe zone, 1407 in the arid steppe zone, and 1540 in the cryoarid ecosystem. Prevalence of the below-ground part in the total biomass structure was revealed for all communities of continental territories. On account of short warm period the total CO2 emission is low. It is maximal from the meadow-subsaline soil in moderately arid forest-steppe and evaluated as equal 1163 g C/m2. The CO2 emission from the meadow-chestnut soil is much lower (633 g C/m2), and falls to the minimal value (353 g C/m2) in the meadow-chernozem cryosoils. The soils appear as the significant depositary of the carbon.Key words: NPP, carbon deposition, meadows, steppe, soil respiration.