Effects of biological crusts on the stability of soil aggregates from different lithologies

Abstract Biological soil crusts (biocrusts) are widespread in karst regions, but their mechanism for enhancing soil aggregate stability across different lithologies remains unclear. This study systematically analyzed changes in aggregate stability and the lithology–vegetation–cover interaction effects under different biocrusts coverages (1%–100%) in planted forests (LDs) and shrub–grasslands (GC) within karst dolomite and clastic areas of southwestern China. The results showed that the development of biocrusts could improve the crust factor and soil physicochemical properties characteristics, with superior crust formation observed on clastic compared to dolomite. Overall, dolomite aggregates exhibited a 21.31% lower percentage aggregation disruption (PAD) and a 5.16% lower fractal dimension ( D ) than clastic, while mean weight diameter and geometric mean diameter increased by 1.16 and 0.94 mm, respectively. Within the same lithology, GC aggregates demonstrated significantly higher stability than those in LDs. Among these factors, silt content emerged as the core determinant of aggregate stability (redundancy analysis explanatory power: 96.01%). Lithology was the absolute dominant factor influencing PAD (contribution rate: 89.74%), with the most pronounced synergistic effect observed in the combination of dolomite + GC + 80%–100% crust cover. These findings provide a scientific basis for addressing rock desertification and enhancing soil and water conservation in karst regions.