Biocrusts enhance erosion resistance of soils derived from two lithologies in the karst region of Southwest China

Soil detachment capacity ( D c ) is a crucial parameter in process-based erosion models. This study investigated moss-covered soils derived from dolomite and clastic rock in Southwest China’s karst region, employing indoor scouring experiments integrated with analyses of moss biocrust growth characteristics, soil properties, and aggregate stability to elucidate the effects of lithology and biocrust coverage on erosion processes. Results indicated that biocrust thickness, roughness, and biomass were significantly influenced by lithology and coverage. Biocrusts on clastic rock exhibited better growth, and their growth factors were more sensitive to coverage gradients than those on dolomite. As coverage increased from 1 to 20 % to 80–100 %, erosion resistance increased significantly, prolonging breakthrough time by 1.11–15.82 times. Biocrust coverage substantially suppressed D c . At 20–40 % coverage, D c significantly decreased by 66.06–83.51 % in dolomite and by 74.07–85.69 % in clastic rock, and soil erosion was nearly negligible under high coverage (>60 %). Coverage and thickness were key regulators of D c for both lithologies (dolomite: total effect = –0.752; clastic: total effect = –0.819). In terms of soil properties, D c in dolomite was primarily governed by sand content, whereas in clastic soils it was jointly regulated by sand content and bulk density. Compared with bare soil, soil rill erodibility decreased by 8.72–99.98 % (dolomite) and 39.60–99.93 % (clastic) with increasing coverage, and clastic biocrusts exhibited greater erosion-reduction efficiency per unit increase in coverage, with thickness identified as the principal erosion-inhibiting factor. This study revealed that biocrusts enhance erosion resistance through synergistic regulation of growth factors and soil properties, providing a foundation for karst erosion modeling and precision conservation.