Effects of Seasonal Freeze-Thaw and Wind Erosion on Runoff and Sediment Yields of Three Loamy Slopes of Loess Plateau, China

Soil erosion is very pronounced during late winter and early spring when frozen soil thaws in the Loess Plateau region of China. The alternation action of seasonal freeze-thaw and wind erosion provide sufficient material sources for water erosion. To quantify the effect of freeze-thaw, wind erosion and their alternate action on runoff and sediment of different slopes. Seasonal freeze-thaw and rainfall tests under different slopes were carried out outdoors and indoors. Results showed that the mean runoff and sediment yield start time of sandy loam (9.84 and 12.75 min) was significant greater than silty loam (8.92 and 9.98 min) and clay loam (4.92 and 5.98 min, P <0.05). The start time of runoff yield after wind erosion, freeze-thaw and alternate action slopes increased by 1.14, 1.35 and 1.62 times, respectively, and the time of runoff and sediment yield under control slope were all the lowest. The runoff rate under different slopes all substantial increased first and then gradually reach to stabilize. Under different slopes, the mean runoff rates of three soils were wind erosion>alternate action>freeze-thaw>control slopes. The mean minimum value occurred at alternate action slope of silty loam (161.56±24.78 g/(m 2 min)), and the maximum at alternate action slope of silty loam (180.88±54.32 g/(m 2 min)). The process of sedimentation was similar to that of runoff. The mean sediment yields values of sandy loam (4.82±0.83 kg) and silty loam (4.66±0.58 kg) were much greater than clay loam (0.65±0.17 kg). In addition, the sediment yields increase magnitude of silty loam under freeze-thaw, wind erosion and their alternate action slopes (58.86%, 17.47% and 58.18%) were higher than sandy loam (29.96%, 3.23% and 44.28%) and clay loam (20.50%, 13.16% and 46.19%). The contribution rate to sediment yield of soil types was the greatest (84.01%), and then freeze-thaw (9.56%) and wind erosion (0.79%)