[Spatial Differentiation Characteristics of Soil Organic Carbon and Its Influencing Factors in Cultivated Land in Major Grain-producing Areas： A Case Study of Hebei Province].

Assessing the spatial differentiation characteristics of soil organic carbon （SOC） in cultivated land in major grain-producing areas is important for regional cultivated land quality management and national food security. We investigated 519 soil profiles of cultivated land in Hebei Province （0-120 cm equally divided into six layers）, and obtained 2961 samples. We used geostatistical methods and spatial exploratory analysis to reveal the spatial distribution pattern of SOC in cultivated land in Hebei Province and the impacts of climate, topography, geomorphology, soil properties, and anthropogenic use on the spatial distribution of SOC in cultivated land soils. The results showed that： ① The SOC content of cultivated land in Hebei Province showed a decreasing trend with the increase in soil depth, with the highest mean value of （SOC） of 9.57 g·kg in A1 （0-20 cm） and the lowest mean value of 4.17 g·kg in A6 （100-120 cm）, and the coefficient of variation showed an increasing trend with the increase in soil depth. ② The SOC at different depths of cultivated land in Hebei Province had similar horizontal spatial distribution characteristics, and in general, showed a trend of being high in the northwest and low in the southeast. ③ Soil texture and topography were the main influencing factors for the spatial variation of SOC in cultivated land in Hebei Province, showing that the more clay-rich the soil texture, the greater the SOC content, and the higher the elevation, the greater the SOC content. Soil pH also influenced the SOC content of the profile. The SOC content of the surface layer is mainly affected by anthropogenic use, whereas the bottom layer is affected by the cumulative temperature.