The Relationship Between Vegetation Characteristics And Sediment Yield And Sediment Yield In Loess Hilly And Gully Region

The synergetic development of different vegetation and soil physical and chemical properties makes the surface soil have a strong ability to retain sediment.It is of great significance to study the response relationship between vegetation and soil and water conservation.In this paper,five vegetation restoration(artificial grassland,wasteland,shrub land,arbor forest,arbor shrub forest)and soil properties under the forest in xindiangou small watershed of Suide in Northern Shaanxi Province were studied.From July to September in 2020,through runoff plot data collection and community sample plot investigation,the vegetation structure and soil properties under different slope positions were studied,Through mathematical statistical analysis,the comprehensive vegetation index evaluation factors and the multiple regression model of runoff and sediment yield were established.The purpose of this study is to explore the relationship between vegetation structure and runoff and sediment yield in the Loess Hilly Region of Northern Shaanxi,and to guide the production practice.The results not only provide the basis for selecting a reasonable vegetation system and building a long-term and efficient vegetation ecological community,but also provide support for the selection of priority areas for restoration and management.The main conclusions are as follows:(1)There are 68 species of plants belonging to 54 genera and 30 families in the five vegetation structure plots,among which Compositae,Leguminosae and Gramineae account for 10%of the total families and 37.04%of the total genera respectively.The Margalef richness index,Simpson dominance index,Shannon Wiener diversity index and Pielou evenness index of herbaceous plants under different vegetation restoration types in the small watershed of Northern Shaanxi Province showed significant differences,but the relationship between different vegetation types was as follows:Shrub land>Wasteland>Arbor shrub mixed forest>Arbor forest>Artificial Grassland(P<0.05).(2)However,the vegetation coverage,biomass and leaf functional traits were significantly higher in the south facing slope than in the north facing slope,with the descending slope having the most advantage,the middle slope taking the second place,and the ascending slope having the worst,showing a gradual decreasing trend(P<0.05).In terms of soil nutrient values,the soil bulk density in the south slope was higher than that in the north slope,and the maximum soil water holding capacity,soil organic carbon,soil total phosphorus and soil total nitrogen in the north slope were higher than those in the south slope,but the change trend of the curve on the slope position was more fluctuating,and the linear law was not obvious(P>0.05).(3)The development of vegetation in small watershed of Loess Hilly and gully region has a significant synergistic and restrictive relationship with soil properties and runoff and sediment yield.Canonical correlation analysis showed that the vegetation parameters of herb layer and shrub layer had more obvious effect on runoff sediment concentration,and the vegetation structure of arbor layer had more close relationship with runoff erosion(P<0.05).RDA ordination showed that there was a significant positive correlation between soil bulk density and runoff sediment concentration,and a strong positive correlation between soil bulk density and runoff erosion(pseudo-F=9.5,P<0.005).There was a significant negative correlation between soil maximum water holding capacity,soil total phosphorus content and runoff sediment concentration,and also a strong negative correlation with runoff erosion(pseudo-F=3.9,P<0.005).(4)Through the linear regression fitting of vegetation comprehensive evaluation index F and runoff sediment concentration and erosion,it is found that there is a significant negative linear correlation between them(R~2=0.87,R~2=0.98).And no matter the South and north slopes have complete vegetation structure layer,the scores of mixed forest and arbor forest are the lowest,which indicates that compared with low shrub land,wasteland and shrub land,it has obvious deficiencies in the function and rationality of vegetation construction,and the benefit of pursuing large arbor forest with high spatial structure coverage in the process of vegetation restoration and reconstruction of small watershed in Northern Shaanxi is very shallow.