Effects of freeze-thaw on soil erosion processes and sediment selectivity under simulated rainfall

The freeze-thaw (FT) processes affect an area of 46.3% in China. It is essential for soil and water conservation and ecological construction to elucidate the mechanisms of the FT processes and its associated soil erosion processes. In this research, we designed the control simulation experiments to promote the understanding of FT-water combined erosion processes. The results showed that the runoff of freeze-thaw slope (FTS) decreased by 8% compared to the control slope (CS), and the total sediment yield of the FTS was 1.10 times that of the CS. The sediment yield rate from the FTS was significantly greater than that from the CS after 9 min of runoff (P < 0.01). Both in FTS and CS treatments, the relationships between cumulative runoff and sediment yield can be fitted well with power functions (R-2 > 0.98, P < 0.01). Significant differences in the mean weight diameter (MWD) values of particles were observed for washed particles and splashed particles between the CS and the FTS treatments in the erosion process (P < 0.05). The mean MWD values under CS were smaller than those under FTS for both washed and splashed particles. The ratio of the absolute value of a regression coefficient between the CS and the FTS was 1.15, being roughly correspondent with the ratio of K between the two treatments. Therefore, the parameter a of the power function between cumulative runoff and sediment yield could be an acceptable indicator for expressing the soil erodibility. In conclusion, the FTS exhibited an increase in soil erosion compared to the CS.