Stability and splash erosion characteristics of lateritic red soil aggregates in the South Subtropical Zone of China

This study analyzed lateritic red soils developed from sand shale and Quaternary red clay to investigate the relationship between aggregate stability and splash erosion characteristics under different land use modes in the South Subtropical Zone of China. The mean weight diameter (MWD) values of soils were ranked slow wetting (SW) > stirring after prewetting (WS) > fast wetting (FW) by the Le Bissonnais (LB) method, indicating that the soil aggregates were least stable under continuous simulated rainfall. The contents of clay, soil organic matter (SOM), and particulate organic carbon (POC) were highly significantly positively correlated with soil stability. There was a highly significant negative correlation between the aggregate splash erosion amounts and MWD values, and the erosion amounts of the orchard and cultivated land soils were 1.20 to 8.38 and 1.53 to 6.68 times those of the woodland soil, respectively. The splash erosion amounts were negatively exponentially correlated with the splash erosion distances, which were mostly distributed at the distance of 0 to 10 cm (accounting for 71.17% to 89.32% of the total splash erosion). The splash erosion amounts on the downhill side were 3.85 to 30.44 times those on the uphill side. The mean weight distance (MWS) values were negatively correlated with the stability of the soil aggregates under the different fragmentation mechanisms, and the correlation coefficients were 0.79, 0.65, and 0.73. During simulated rainfall, the splash erosion rates first increased, then decreased and tended to be stable after reaching the peak, and the rainfall duration to reach the peak decreased with increasing rainfall intensity. At the rainfall intensities of 30 to 60 mm h−1, the splash erosion rates peaked at 24 to 36 min. At the rainfall intensities of 90 to 120 mm h−1, the splash erosion rates peaked at 12 to 30 min. With increasing rainfall duration, the amounts of large aggregates in the splash transport increased. These results can provide a theoretical basis for the formulation of soil and water conservation measures in the South Subtropical Zone of China.