[Spatial Differentiation of Soil Organic Carbon Density and Influencing Factors in Typical Croplands of China].

Cropland soil organic carbon density (SOCD) is an important indicator for measuring soil fertility and soil quality. To understand the spatial differentiation characteristics of cropland SOCD and its influencing factors across China, a dataset on the cropland SOCD of 19 typical stations during 2005-2015 was collected from the China Ecosystem Research Network. The geodetector method was used to analyze the influencing factors affecting the spatial patterns of cropland SOCD. The results indicated that the mean cropland SOCD ranged from 0.83 kg·m to 4.97 kg·m in different stations across China, and was higher in humid monsoon regions than in arid and semi-arid regions. Under different land use patterns, the SOCD of paddy fields was higher than that of other croplands and showed a tendency of significant increase from 2005 to 2015, reaching 0.13 kg·(m·a). The soil physical and chemical properties and precipitation were important influencing factors that affected the spatial patterns of cropland SOCD. In particular, the soil alkaline nitrogen content had the greatest impact on the cropland SOCD patterns. Furthermore, the interaction forces between the soil alkaline nitrogen content and latitude, soil type, precipitation, and soil pH were clearly strengthened. The findings can provide an important scientific basis for reducing cropland greenhouse gas emissions and increasing soil carbon sequestration across China.