Changes of soil organic carbon of grassland in the Xilinguole,Inner Mongolia from 2000 to 2007

Based on data sets of soil organic carbon(SOC) extracted from the literature about grassland area and different managements,the SOC changes of grassland in the Xilinguole,Inner Mongolia from 2000 to 2007 were estimated to understand the contribution of grassland management on SOC by two approaches,in which one was the IPCC Tier 2,and the other was transfer matrix of SOC under various managements.The results of this study showed that SOC of grassland in the Xilinguole increased by 20.85-29.80 Tg with an average rate of 2.61-3.72 Tg/a from 2000 to 2007.The increment of SOC in the Dongwuzhumuqin,Xiwuzhumuqin,Sunitezuo,Suniteyou and Abaga,and Xilinhaote city was more than 80% of total increment of SOC.Correlation analysis indicated the SOC estimated by the IPCC Tier 2 showed a similar trend with those estimated by transfer matrix approach,while the total SOC estimated by the IPCC Tier 2 was approximately one third of those estimated by transfer matrix approach.The estimated annual SOC was not consistent between two approaches.The annual increment of SOC before the third year was greater than that after the third year when the IPCC Tier 2 was employed,while the increment of SOC after the fifth year was higher than that before the third year when the transfer matrix approach was employed.