不同尺度下冻融作用对东北黑土区产流产沙的影响

通过对东北黑土区坡面8年和小流域7年的降雨产流产沙过程观测,对比每年受冻融作用影响的降雨和其余不受冻融作用影响的降雨产流产沙的特征,研究冻融作用在坡面和小流域尺度上对东北黑土区产流产沙的影响,为东北黑土区在冻融作用下多尺度土壤侵蚀定量评价及其转换模型的建立提供科学依据。结果表明:冻融作用减小了坡面和小流域的产流,径流系数分别减小0.07和0.03,坡面产流延迟71.7%,而小流域无明显延迟。坡面和小流域土壤流失量、土壤可蚀性K值及含沙量均显著增加,更易在较小降雨侵蚀力下产生较大流失量;与不受冻融的降雨事件相比,受冻融影响的降雨事件因径流减弱,在相同降雨量下的侵蚀量低,而在相同径流深下的侵蚀量高。冻融作用在径流较小时对坡面细沟的发育及产沙影响明显,在径流较大时对小流域切沟中松散堆积物的搬运及产沙影响明显。

Effects of Freezing and Thawing on Runoff and Sediment Yield in the Black Soil Region of Northeast China at Different Scales

Based on runoff and sediment yield at plot and small watershed scales by field monitoring of 8 years and 7 years respectively in the black soil region of Northeast China,the characteristics of runoff and sediment yield of the first two rainfall events and those of the rest events were compared,which represented the runoff and sediment yield that was influenced and not influenced by freezing and thawing respectively.Results showed that with the effects of freezing and thawing,the runoff coefficient reduced by 0.07 and 0.03 at plot and small watershed scale respectively.Initial abstraction duration increased by 71.7％ at slope scale;while,there was no obvious increase at small watershed scale.Soil loss,soil erodibility and sediment concentration increased significantly at both scales under freezing and thawing,and soil erosion was more likely to occured.When the runoff was small,the sediment amount of the rainfall events with freezing and thawing was smaller than that of the rainfall events without it.Compared to those rainfall events without freezing and thawing,the rainfall events with freezing and thawing led to the runoff reduction.As a result,sediment amount of the rainfall events with freezing and thawing was lower at the same rainfall,while it was higher at the same runoff.Freezing and thawing had a more evident effect on rill development and sediment amount at plot scale when runoff was small,as well as capacity of the loose deposits transportation and sediment amount at small watershed scale when runoff was large.The results provide a scientific basis for the quantitative evaluation and transformation model of soil erosion with freezing and thawing in the black soil region of Northeast China.