Estimating soil organic carbon sequestration potential in the Chinese Mollisols region

Mollisols region of China is a ballast stone of Chinese food security. In this study, 484 soil organic carbon (SOC) data points from the documented soil surface (0-20 cm) samples in the typical Chinese Mollisols region were selected. The regional soil fertility was divided into high, medium, and low levels based on the SOC content from the long-term positioning fertilization stations in Shenyang, Harbin, and Hailun of Northeast China. Furthermore, the regional SOC balance point (SOCb) model was built driven by the factors of annual mean temperature, annual precipitation, annual effective accumulative temperature, the ratio of precipitation and temperature, soil clay content, and pH. Using geographic information systems (GIS) interpolation method, the regional mean SOCb and SOC sequestration potential (SOCsp) at the SOCb's status were simulated to be 40.10 g kg-1 and 10.71 kg m-2, respectively. Moreover, the SOC content increased (SOCc) and the SOC sequestration capacity increased of medium- or low-fertility soil were evaluated by GIS subtraction. Consequently, the means of SOCc in medium- and low-fertility soils could be 16.88 g kg-1 and 26.79 g kg-1, respectively. Furthermore, the means of SOCsp in medium- and low-fertility soils could be 4.30 kg m-2 and 7.43 kg m-2, respectively. The sensitivity analysis of this model showed that the high SOCb area was distributed in study region with low temperature, dry, high clay content, and low pH. The results provide an actual perspective on estimating regional SOCsp and soil fertility promotion target induced by the different soil fertility levels. A soil organic carbon (SOC) balance point concept was innovatively put forward. The SOC sequestration potential of typical Chinese Mollisols region was estimated based on the SOC balance point. Both regional SOC content increased and sequestration capacity increased were estimated.