Responses of soil aggregate stability to organic C and total N as controlled by land-use type in a region of south China affected by sheet erosion

Soil aggregate stability is considered as one of the most sensitive parameters that reflect soil structure and quality, which is significantly influenced by soil organic carbon (OC) and total nitrogen (TN). However, the responses of soil OC and TN contents in both bulk soils and aggregates to aggregate stability as affected by landuses remain unclear, especially under sheet erosion condition. Thus, aiming to investigate the effects of different land-use types on soil aggregate stability, aggregate-associated OC and TN contents and the relationships between them under sheet erosion condition in south subtropical zone of China, soil samples from four land-use types were collected at soil depths of 0-10, 10-20 and 20-30 cm, respectively. Results showed that soil water-stable aggregate content (WSA), mean weighted diameter (MWD), geometric mean diameter (GMD), aggregate-associated OC and TN were highest in woodland soil and showed significant differences among different land-use types (P < 0.05), which were mainly because of the differences on aggregate size distributions induced by soil erosion. Soil aggregate-associated OC and TN contents decreased with the increases of aggregate sizes. In addition, soil aggregate-associated OC and TN contents were negatively correlated with aggregate sizes, because of the strong bonding ability among OC, TN, clay particles and aggregates. Moreover, the interactions among soil aggregate-associated OC, TN and physicochemical properties contributed to 81.7 % of aggregate stability, which highlighted the vital role of OC and TN on maintaining soil aggregate stability under sheet erosion condition. Therefore, appropriate agricultural and engineering strategies focusing on the enhancement of aggregate-associated OC and TN should be carried out to maintain soil aggregate stability and reduce erodibility under global sheet erosion condition.