Effect of seasonal freeze-thaw on the detachment capacity of aeolian sandy soil in Dongliugou watershed
[Background] Soil detachment is the initial phase of soil erosion,and is of great significance to studies in regions that are characterized by seasonal freeze-thaw regimes.However,this process remains unclear because limited research on soil physical properties and soil detachment capacity has been carried out to date under freeze-thaw conditions.Thus,the aims of this study were to determine and compare the effects of slope gradient,flow discharge,moisture content,soil depth and freeze-thaw cycles on soil detachment capacity.[Methods] The soil samples were collected from the 0-20 cm soil layer in an abandoned cropland.It is located in Dalad Banner,Inner Mongolia which is the crisscross region of Hobq Desert and the Loess Plateau.In this study,in order to elucidate the effects of freeze-thaw on aeolian sandy soil detachment capacity,a series of artificial freeze-thaw simulations in combination with flume experiments were conducted by using the orthogonal method.[Results] 1) Slope,flow discharge,moisture,freeze-thaw cycles and soil depth had significant influence on soil detachment capacity (P < 0.05).The sensitivity degree of each factor on aeolian sandy soil detachment capacity was:slope > flow > freeze-thaw cycles > soil moisture content > soil depth,and slope and flow discharge were main affecting factors.2) The aeolian sandy soil detachment capacity was linearly correlated with flow discharge and slope (R2 > 0.94).The critical value of flow discharge and slope affecting aeolian sandy soil detachment capacity was 0.07 L/min and 6 %,respectively.3) Soil moisture,freeze-thaw cycles and soil thawing depth influenced aeolian sandy soil detachment capacity indirectly by changing soil physical properties.The process,range and degree of freeze-thaw were restricted by soil moisture content and occurrence condition.If soil moisture content was too higher or lower,it would lead to the increase of aeolian sandy soil detachment capacity.When the soil moisture was 6%,the aeolian sandy soil detachment capacity reached the minimum value.Freeze-thaw cycles resulted in the redistribution of soil moisture.The effect of soil depth on soil detachment capacity was basically consistent with soil moisture content,and aeolian sandy soil detachment capacity of middle depth was the smallest.The aeolian sandy soil detachment capacity increased obviously with the number of freeze-thaw cycles increased,but gradually tended to flat trend after 10th cycles.[Conclusions] The above results indicated that seasonal freeze-thaw increased aeolian sandy soil detachment capacity and it will lead to the increase of soil erosion in spring of the seasonal freeze-thaw area.This research results may provide reference for the study of erosion mechanism of seasonal freeze-thaw areas.The effect of freeze-thaw on the soil detachment capacity,however,requires further investigation in regions where this process occurs seasonally.