Effects of grassland managements on soil organic carbon and microbial biomass carbon

In order to evaluate the carbon source/carbon sink function of grassland and explore the sustainable grassland management measures, the combined methods of field sampling and laboratory analysis were employed to analyze the variation of soil organic carbon (SOC) and soil microbial biomass carbon (SMBC) in Xilingol typical grassland in Inner Mongolia. The effects of different management and grazing measures on the distribution and carbon reserves of SOC and SMBC were discussed. The studied measures included fenced enclosure for 29 years (WF29), fenced enclosure for 8 years (WF8), filling-up Medicago sativa (RA), filling-up Leymus chinensis (RC), and three grazing measures . The surface soil layer was higher carbon pool because the SOC and SMBC in the soil profile decreased with soil depth increasing. The SOC and SMBC of WF8 and WF29 were higher than that of HG in root system soil layer (0-30 cm). There were significantly positive effects of WF8 management on SMBC and SOC. There was significantly positive correlation (P0.05) between SOC and SMBC. The variations of SMBC not only reflect the changes of SOC, but aslo reflect the changes of soil organic carbon pool. The total SOC and SMBC carbon reserves were 788.84 Gg C and 9.47 Gg C in Xilinhot, respectively. The SOC and SMBC carbon reserves were highest under fenced enclosure for 8 years (661.76 Gg C, 6.76 Gg C), and lowest under the artificial filling-up measures (0.61 Gg C, 5.73 t C). SOC and SMBC were the indicators of soil fertility and soil quality and important evaluation index of grassland carbon sink.