The Evaluation Of The Soil Conservation Function Of Shrub And Grassland System Based On The In Vest Model In Loess Plateau

The Loess Plateau is a particularly weak and sensitive ecological environment.Under the long-term erosion of water flow,it has become one of the most severely soil erosion areas,seriously affecting and restricting the ecological security,economic and social sustainability of the region.Soil conservation is the primary task of the Loess Plateau.Soil conservation is also the dominant function of ecosystem services in the region.The shrub and grassland system is a type of vegetation that plays an important role in soil conservation in the Loess Plateau.Assessing its soil conservation function is of great significance for understanding the important position and role of shrub and grassland system.This study takes the example of Anding District,Dingxi City,by using the InVEST model and ArcGIS software,to study the soil conservation function of the shrub and grassland system in the hilly area of the Loess Plateau in 2017,provide decision-making basis for the formulation of ecological protection policies in the Loess Plateau.The research results are as follows:First,using the Wischmeier formula to calculate the rainfall erosivity R in Anding District is between146-881146-881（MJ·mm/hm²·h·a）,through the ArcGIS analysis,the rainfall erosivity increases from north to south,the high value of rainfall erosivity appears in the southern part of the study area.Second,using the EPIC model to calculate the soil corrosion K in the Anding District is between 0.0133-0.0177(t·hm²·h·hm^-2·MJ^-1·mm^-1).Through the ArcGIS analysis,the soil corrosion K is reduced from north to south.Third,using the InVEST model,the actual soil erosion in Anding District in 2017was calculated to be 9.53×10⁶t,average soil erosion per unit area in Anding District was 26.4t/hm²t.Soil slight erosion and mild erosion accounted for 98.96%of the total area and 70.4%of total erosion;moderate erosion,strong erosion,extremely strong erosion and severe erosion accounted for 1.04%of the total area and 20.6%of total erosion.It indicates that the soil erosion in Anding District is mainly characterized by slight and mild erosion.Fourth,According to the order of land use,the actual soil erosion from large to small is:cultivated land（768.07×10⁴t）>natural grassland（129.19×10⁴t）>construction land（30.1×10⁴t）>unused land（14.77×10⁴t）>shrub and grassland system（9.69×10⁴t）>forest land（1.16×10⁴t）>water area（0.079×10⁴t）.The area of cultivated land accounts for 32.69%of the total region,the actual soil erosion and erosion intensity are the largest,the soil erosion intensity reaches 64.99t/hm²,and the actual soil erosion reaches 7.68×10⁶t,accounting for 80.59%of the total actual soil erosion in the region.The area of the shrub and grassland system accounts for 29.7%of the total region,the soil erosion intensity is 0.9t/hm²,the actual soil erosion is9.69×10⁴t,and the actual soil erosion for only 1.02%of the total actual soil erosion in this area.Comparing the unit area,the actual soil erosion of the shrub and grassland system is only 1.38%of the cultivated land.Fifth,the calculation results of soil conservation volume showed that the average soil conservation volume per unit area in Anding District was 167.3t/hm²t.Among them,the soil conservation volume per unit area of the shrub and grassland system was the highest,reaching 308.76t/hm²,which was 1.85 times of the average level.The total soil conservation volume in the region was 6.04×10⁷t,of which the shrub and grassland system reached 33.1×10⁶t,accounting for 54%of the total soil conservation volume.According to the order of land use,the soil conservation volume from large to small is:shrub and grassland system（3310.21×10⁴t）>natural grassland（2042.03×10⁴t）>cultivated land（606.9×10⁴t）>construction land（50.17×10⁴t）>forest land（23.56×10⁴t）>unused land（4.55×10⁴t）>water area（0.54×10⁴t）.