Land use conversion and lithology impacts soil aggregate stability in subtropical China

Soil aggregate stability is one of the most important indicators of soil structure and soil degradation vulnerability, and it is the dominant factor controlling hillslope soil erosion in the subtropical Ultisols region of China. However, few studies have investigated the synergistic effects of land use conversion and lithology on soil aggregate stability, especially in subtropical Ultisols region of China where soil erosion is a serious concern. Soil samples from 0 to 100 cm depth at increments of 20 cm were collected from four typical land use types (natural forest, artificial forest, orchard, and cropland) and two lithologies (granite and slate) to determine soil aggregate stability using the Le Bissonnais' and Yoder' methods on Ultisols from subtropical China. Results indicated that both land use type and lithology significantly influenced the soil aggregate stability. Specifically, in different soil depths of 0-100 cm, land use changes from natural forest to orchard and cropland significantly decreased the aggregate stability, thus increasing soil erodibility. Following the conversion of natural forest to artificial forest generally enhanced soil stability and resistance to flowing water erosion. For lithology, the slate soil was more resistant to erosion than granite soil. The generalized linear model can explain >60% of the total variation in soil aggregate stability, and the effect of land use on aggregate stability was greater than lithology. Compared with the Yoder' wet-sieving method, the Le Bissonnais method was better at characterizing soil aggregate stability among land uses and lithology, and therefore should be considered as a preferred method in future studies in the subtropical Ultisols region of China.