Research of changing characteristics and control factors of farmland topsoil organic carbon in China

Through collecting 966 samples of measured data of farmland topsoil organic carbon,as well as temperature and precipitation data from 1980 to 2006 of China,this paper analyzed changing characteristics of farmland soil organic carbon of China,discussed the reasons of change and development trends,and analyzed the differences of carbon sequestration ability of the temperature and rainfall on the paddy soil and dry soil,and the affection of temperature and rainfall on the soil organic carbon in different regions.The results show that farmland topsoil organic carbon of measured points presents upward trend overall,with 79% of increase samples mainly concentrated in the rise of 0~3% range.Soil organic carbon content was subject to climatic factors of temperature and precipitation,and the combination of hydrothermal conditions.Over the past 20 years,the distribution patterns of farmland topsoil organic carbon content remains unchanged.The change of farmland soil organic carbon was mainly affected by the impact of human activities.The difference of land use on soil carbon sequestration was significant,the level paddy soil organic carbon was significantly higher than the dry land,and the content of paddy topsoil organic carbon was 175%~176% of that of dry land.