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 on the Loess Plateau of China. The alternating action of seasonal freeze-thaw and wind erosion provides sufficient material sources for water erosion in the rainy season, greatly increasing the risk and intensity of soil erosion. To quantify the effect of seasonal freeze-thaw, wind erosion and their alternating action on runoff and sediment of different slopes, rainfall tests of different slopes (control, seasonal freeze-thaw, wind erosion and seasonal freeze-thaw + wind erosion of sandy loam, silty loam and clay loam) were carried out indoors. The results showed that the mean runoff and sediment yield start times of sandy loam (9.84 and 12.75 min) were significantly greater than those of 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 alternating action slopes increased by 1.14, 1.35 and 1.62 times, respectively, and the time of runoff and sediment yield on the control slope were all the lowest. The runoff rates under different slopes all substantially increased first and then gradually stabilized. On different slopes, the mean runoff rates of the three soils decreased in the order of wind erosion > alternating action > freeze-thaw > control slopes. The minimum value occurred on the alternating action slope with silty loam (161.56 & PLUSMN; 24.78 g/(m2 min)), and the maximum occurred on the wind erosion slope with clay loam (360.77 & PLUSMN; 35.98 g/(m2 min)). The process of sedimentation was similar to that of runoff. The mean sediment yield values of sandy loam (4.82 & PLUSMN; 0.83 kg) and silty loam (4.66 & PLUSMN; 0.58 kg) were much greater than those of clay loam (0.65 & PLUSMN; 0.17 kg). In addition, the sediment yield increase magnitudes of silty loam under freeze-thaw, wind erosion and their alternating action slopes (58.86 %, 17.47 % and 58.18 %, respectively) were higher than those of sandy loam (29.96 %, 3.23 % and 44.28 %, respectively) and clay loam (20.50 %, 13.16 % and 46.19 %, respectively). The contribution rate to sediment yield of soil types was greatest (84.01 %), followed by freeze-thaw (9.56 %) and wind erosion (0.79 %). This study can provide a reference for the study of compound erosional mechanisms and soil and water conservation in seasonal freezing-thaw zones.

Automated summary

Soil erosion is more pronounced during late winter and early spring on the Loess Plateau of China, due to the alternating action of seasonal freeze-thaw and wind erosion. This study found that different slopes and soil types have a significant impact on runoff and sediment yield, with sandy loam having the highest mean runoff and sediment yield start times.