Changes in soil water repellency and soil erosion resistance as affected by land uses in karst environments

Soil water repellency (SWR) exists in various soil ecosystems and can interrupt water infiltration and cause soil erosion. Anthropogenic land-use change can cause shifts in SWR and soil erosion resistance (SER) in sensitive soils. However, the direction and magnitude of these shifts in SWR and SER and their interrelations remain largely unclear. This study examined the changes in SWR, soil erodibility (K), and aggregate fractions in different land uses of a karst trough valley in southwest China. Soil samples were gathered from five land uses: cropland (CL), orchard (OP), secondary forest (SF), grassland (GL), and riverbank (RB), using a 1000 m × 1000 m grid, resulting in 210 sampling sites. Results showed that the water drop penetration time was significantly higher by 86.43%, 68.85%, and 71.47% in the SF, OP, and RB than in the CL, respectively (p < 0.05). The soil organic carbon (SOC) was the greatest in the SF and the lowest in the GL and CL (p < 0.05). The 1000-250 μm aggregate fraction, mean weight diameter (MWD), and geometric mean diameter (GMD) varied markedly among the different land uses (p < 0.05). The silt content, fractal dimension (D), and K were markedly lower in the RB than in the CL, OP, SF and GL (p < 0.05). The SWR had pronouncedly positive correlations with the SOC and 1000-250 μm aggregate fraction (p < 0.05). The K displayed a negative correlation with the GMD but a positive correlation with the D (p < 0.05). The structural equation modeling analysis revealed that the SOC was affected positively by the silt content and the 1000-250 μm aggregate fraction and negatively by the K. These factors directly regulated the SWR. Our results shed light on the mechanisms of land use changes impacting the SWR, SER and other soil properties in karst environments.