Study On Soil And Water Conservation Ofvegetation In Loess Plateau

Soil erosion is one of the main environmental problems in the loess plateau area,which seriously threatens the livelihood and production activities of the local people.Vegetation can reduce soil erosion and maintain ecological balance,so vegetation construction is one of the important measures to control soil erosion in the loess plateau area.It is of great significance for the vegetation construction in the loess plateau region to understand the law of soil and water conservation by studying the variation rules of runoff and sediment yield of different vegetation coverage and vegetation structure as well as the benefits of reducing water and sediment.Due to different vegetation in the study of soil and water protection effect is influenced by experimental condition the results differ greatly,therefore,this study collected 68articles on the loess plateau vegetation for soil and water conservation research literature,using the method of integrated analysis,system analysis under different rainfall conditions of vegetation coverage and vegetation structure and the change rule of flow and sediment yield of different vegetation coverage and the structural factors of vegetation index change tendency of flow and sediment reduction benefit,and obtained the following main results:(1)The slope runoff decreases with the increase of vegetation coverage.When the vegetation coverage is about 40-50%,the yield and flow rate change,and the vegetation plays an effective role in soil and water conservation.According to the regression analysis,yield flow and vegetation coverage show a binomial relationship,that is,y=ax~2+bx+c(where y represents yield flow;X is vegetation coverage;a,b and c are the coefficients of the equation).The trend of reducing flow benefit can be divided into three stages.The first stage is the rapid increase stage;The second stage is the steady increase stage;The third stage is the descending stage.The effective coverage of vegetation is between 40-50%and the critical coverage is between70-80%.Through regression analysis,it is found that the relationship between flow reduction benefit and vegetation coverage is logarithmic,that is,y=aln(x)+b(where y represents flow reduction benefit;X is vegetation coverage;a and b both represent the coefficients of the equation).(2)The change of sediment yield was consistent with the change of runoff yield,and also decreased with the increase of vegetation coverage.When vegetation coverage increases from 0 to 40-50%,sediment yield decreases significantly with the increase of vegetation coverage.When vegetation coverage exceeds 50%,sediment yield decreases to a minimum of 70-80%.When vegetation coverage exceeds 80%,sediment yield tends to be stable.Regression analysis of sediment yield and vegetation coverage shows that the binomial relationship between sediment yield and vegetation coverage is obtained,that is,y=ax~2+bx+c(where y represents sediment yield;X is vegetation coverage;a,b and c are the coefficients of the equation).The variation of sediment reduction benefits of different vegetation cover can be roughly divided into two stages.The first stage is the rapid increase stage;The second stage is the steady increase stage.According to the regression analysis,the relationship between yield and vegetation coverage is logarithmic,that is,y=aln(x)+b(where y represents the benefit of sediment reduction;X is vegetation coverage;A and b both represent the coefficients of the equation).(3)Different vegetation structures have differences in playing the role of soil and water conservation.According to the field observation results,the order of the average runoff yield and sediment yield of different vegetation structures is as follows:single structure>double layer structure>triple layer structure.The richer vertical structure of vegetation community,the lower degree of soil erosion.(4)The higher structural vegetation factor index(C_s)of vegetation community,the better effect of soil and water conservation.The efficiency of flow reduction and sediment reduction increased with the increase of structural vegetation factor index.he change trend can be divided into three stages:the first stage is the stage of rapid growth.When C_sincreases from 0 to 15%,the efficiency of flow reduction and sediment reduction increases rapidly.The second stage is the stage of steady growth.The efficiency of reducing flow and sediment of C_sgrows slowly between 15-25%.The third stage is a stable stage.When C_sexceeds 25%,the efficiency of flow and sediment reduction tends to be stable.According to the regression analysis,both the flow reduction and sediment reduction benefit and the structural vegetation factor index show a logarithmic relationship,that is,y=aln(x)+b type(where y represents the flow reduction benefit or sediment reduction benefit;X represents the structural vegetation factor index;a and b both represent the coefficients of the equation).