| The low hilly area of red soil in southern China is one of the major soil and water loss areas in China.It is of great significance to study the change law of soil erosion and the effect of water and soil conservation in the region on the protection of the environment and ecosystem services.Standard runoff plots are the basic unit for exploring the occurrence and development of soil erosion and the effects of water and soil loss control measures.On this basis,the results of the study have important scientific significance for the prevention and control of large-scale soil erosion.This study takes Yueyang Xianan standard runoff plots as the study area from the typical hilly areas of red soil in southern China.Based on the data of rainfall,runoff and sediment in standard runoff plots from 2015 to 2016,the effects of topography and rainfall on the dynamic characteristics of soil erosion were analyzed,and the effects of typical control models on soil and water conservation were studied.The results of the study indicate:(1)Rainfall in the low hilly areas of red soil in southern China showed a single peak-type curve during the year,and rainfall was mainly concentrated in April-July.According to the result of K-means clustering,the rainfall in this area can be divided into three rain types: A,B,and C.Among them,the B rain type has the characteristics of strong rain,short duration,and small rainfall.The C rain type has the characteristics of light rain,long duration,and heavy rainfall,and the A rain type character is between the B and C rain patterns.For the three types of rainfall,the slope runoff is A>B>C rain.For the three types of rain,the amount of sediment on the slope is in the S1(slope to ladder + fruit forest)and S2(cross-slope ridge + crop)plots is A>C>B rain type,and it is C>A>B rain type in S3(landfall slope + a small amount Herbs)plot.Seasonal distribution characteristics of runoff and sediment are obvious for different rain patterns.Runoff and sediment concentrate mainly in April and June for the A-Rain,and they concentrate mainly in May for the B-Rain.However,the distribution of runoff and sediment is relatively influenced by the underlying surface for the C rain pattern.(2)Runoff and sediment transport in the slope area have obvious response to slope,and they increase with increasing slope(5~15°).Among them,the 10° slope runoff is 1.57 and 2.5 times that of 5°slope in the S2 and S3 plots,respectively,and the 15°slope runoff is 1.23 and 5.47 times that of 10° slope,respectively.On the other hand,the sediment loss at the 10° slope of S2 and S3 plots was 5.82 and 3.94 times that of the 5° plot,and that of the 15° plot was 2.12 and 22.37 times that of the 10° plot,respectively.The rainfall infiltration rate on the slope decreases as the slope increases.The infiltration rates of S2 and S3 plots from 5° to 10° decreased by 13.9% and 7.7%,respectively,while the gradients from 10° to 15° decreased by 11.8% and 35.8%,respectively.There was a significant positive correlation between runoff and sediment at different slopes and maximum 30-minute rain intensity I30 and rainfall(P<0.05,r>0).However,it is significantly different from the significant level of rainfall time,and both the significant level and the correlation coefficient are greatly affected by the slope.(3)Different control modes have obvious soil and water conservation effects.The annual inner runoff distribution uniformity D is 0.791,0.733,and 0.856 for the S1,S2,and S3 plots,respectively.In addition,the runoff and sediment load are both S3>S1>S2.Among them,the runoff volume of S3 plot was 1.79 and 2.36 times that of S1 and S2 plots,and the sediment volume was 2.90 and 3.83 times,respectively.The runoff and sediment of S1 plot are 1.32 times that of S2 plot.In the reduction of runoff from rainfall,the average reduction rate of S2 reached 77.0%,and the average reduction rate of S1 was 49.8%.In the reduction of sediment from rainfall,the average reduction rate of S2 reached 83.8%,and the average reduction rate of S1 was 56%. |
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