Spatial distribution of soil organic carbon and its influencing factors at different soil depths in a semiarid region of China

Studying spatial variability of soil organic carbon (SOC) is crucial for understanding the largest active carbon pool in terrestrial ecosystems. The main objectives ofves of this study were (1) to analyze the spatial pattern of SOC at different depths and (2) to define the soil properties affecting the spatial patterns of SOC at different depths. A total of 910 soil samples were collected at different locations and soil layers in a semiarid zone (3800 km²) of northeastern China. A geostatistical approach was used to predict and map SOC at different depths while the soil properties affecting the spatial patterns of SOC were analyzed by using canonical correspondence analysis. As expected, SOC content decreased gradually with depth and such a SOC decrease depended on soil type, which resulted the main factor affecting horizontal and vertical distributions of SOC content. Slope and bulk density exhibited a negative correlation with SOC content, whereas vegetation index, soil moisture content, elevation, and aspect showed a positive correlation. Sensitivity of SOC to influencing factors differed with increasing soil depth. SOC was significantly correlated with vegetation and bulk density on topsoil, while soil moisture and aspect played an important role in controlling SOC with increasing depth.