[Spatial distribution and influencing factors of soil dissolved organic carbon in Dongting Lake Basin]

Soil dissolved organic carbon (DOC) is a crucial component of terrestrial carbon pool, and its spatial distribution characteristics are of significant importance for the regulation of regional carbon sequestration and the enhancement of carbon sink. Taking the Dongting Lake Basin as the research area, by utilizing geostatistics, correlation analysis, and GIS technology, we analyzed the spatial distribution of topsoil (0-10 cm) DOC and its correlation with environmental variables, including land use types, soil physicochemical properties, and topography. The results showed that: 1) Soil DOC content in the Dongting Lake Basin ranged from 4.31 to 271.29 mg·kg^-1, with an average value of 78.46 mg·kg^-1 and a coefficient of variation of 52.1%, indicating a moderate level of variability. 2) Soil DOC generally exhibited a patchy distribution with a decreasing trend from south to north, showing a moderate spatial autocorrelation with higher variability in the 45°, 90°, and 135° directions due to the joint influences of structural and random factors. 3) Land use patterns, rainfall, slope, soil organic carbon, total nitrogen, and cation exchange capacity were significantly correlated with DOC. Soil physicochemical properties and land use patterns were the main controlling factors affecting the spatial differentiation of soil DOC, with explanation rates of 23.7% and 22.8%, respectively. Our findings would provide a scientific basis for soil carbon sink management and carbon cycle balance in the Dongting Lake Basin.