Surface soil water content and its controlling factors in a small karst catchment

Spatial distribution of soil water content (SWC) plays an important role in soil hydrological processes. Karst areas are especially heterogeneous with respect to soil distribution and properties and have not been adequately studied. The purpose of this study was to characterize the surface SWC and to discuss its controlling factors in a small karst catchment in Guangxi, China. SWC was measured using the gravimetric method along seven line-transects crossing farmland, shrub-grassland, shrubland and forestland, as well as hillslopes and depressions. Soil bulk density, capillary porosity, macroporosity, rock fragment content (RC), soil organic carbon and soil texture of the soil samples were also determined. Regression and sensitivity analysis methods were used to analyze the influence of soil properties on SWC in both the wet and dry season. Generally, SWC was significantly higher in depressions than on hillslopes. In the shrub-grassland and shrubland, SWC decreased with increasing elevation, whereas in the forestland, no obvious trend along the transect was found. Soil porosity, RC and soil texture were three main soil properties that influenced SWC significantly. Moreover, the distribution of SWC along the line-transects were coincidence with that of these soil properties. The results document the spatial distribution of SWC in a karst catchment in southwest China, laying a foundation for a better understanding and modeling of hydrological processes in this complex landform.