Soil Carbon Balance in a Native Temperate Grassland in the Xilin River Basin of Inner Mongolia

Based on historical data and field investigation, some major fluxes and reserves of carbon were estimated, and a tentative analysis of the soil carbon balance was made in a native grassland community in the Xilin River basin of Inner Mongolia. Major results were reported as follows: 1) Annual average carbon input from above_ground biomass production was 79.8 g C·m -2 ·a -1 , and from root biomass to 30 cm depth averaged 311.9 g C·m -2 ·a -1 . The summed mean annual carbon input of shoot and root materials in the study site was approximately 391.7 g C·m -2 ·a -1 . 2) The annual amount of above_ground biomass consumed by insects averaged 14.7 g C·m -2 ·a -1 , and the carbon output by leaching or light_chemical oxidation was 3.2 g C·m -2 ·a -1 . The annual evolution rate of CO 2 from net soil respiration averaged 346.9 g C·m -2 ·a -1 , and the summed mean annual output was approximately 364.8 g C·m -2 ·a -1 . 3) A mature, steady_state system could be assumed for the community for which growth and decay were approximately in balance, with a net carbon accumulation of about 26.9 g C·m -2 ·a -1 . Based on the soil organic carbon density of the field, the turnover rate of soil carbon in 0-30 cm depth was calculated to be 6.2%, with a turnover time of 16 years.