| As one of the important regulation services provided by ecosystem services,soil conservation plays an irreplaceable role in alleviating human-land relations,ensuring regional food security,rationally planning the use of land resources in the region,and maintaining ecological security.Based on the land use/cover data,this study analyzes the land use changes in the Koshi River Basin from 2000 to 2017.Based on this,combined with meteorological data,soil data,NDVI data and DEM data,the InVEST model is applied to soil erosion in the Koshi River Basin.Quantitative evaluation of the spatial and temporal evolution characteristics of soil conservation service functions,and the effects of land use change on watershed soil erosion and soil conservation capacity are discussed.The main conclusions are as follows:(1)Significant changes in land use in the Koshi River Basin from 2000 to 2017,mainly manifested by a significant reduction in grassland and arable land,a slight decrease in forest land area,and significant expansion in other land use types.During the 17 years,grassland was mostly concentrated in slopes with an altitude of 4000?5500m and a slope of<15°,and the area decreased significantly.The cultivated land was mainly distributed in areas with an altitude of less than 2000m and a slope of<5°,and the area under 500m increased significantly.It is distributed on slopes below 5000m and slopes<5°,30?40°,>45°,the area change is not significant;construction land is mainly concentrated in areas below 500m and 1000?1500m,slope<10°,of which altitude the expansion of cities below 500m is obvious.From the perspective of comprehensive land use dynamics,land use change in the river basin from 2010 to 2017was significantly faster than that from 2000 to 2010.(2)From 2000 to 2017,the total soil erosion in the Koshi River Basin increased from 317.69×10~8t to 445.44×10~8t.The high-value areas of soil erosion were mostly concentrated in the northern regions of Sindhupalchok,Dolakha,Solukhumbu,Sankhuwasabha,and Tapejung in Nepal,and the Tibet Autonomous Region of China.Northeast of Tingri County,north of Dinggye County,and southwest of Sakya County.Low-value areas are mostly located in the county territory of the Terai Plain in Nepal and Nylam and Gamba counties in China.In 2000?2017,the soil erosion volume and soil erosion modulus in the study area showed an increase and then a decrease with the elevation.In addition,with the increasing slope,the amount of soil erosion in the study area first decreased and increased,but the soil erosion modulus continued to increase.From the perspective of soil erosion intensity transfer,almost all soil erosion intensity types in the two periods of 2000?2010 and 2010?2017 showed a trend of shifting to adjacent erosion intensities.high.In the 17 years,the growth trend of slight and lightly eroded areas in the Koshi River Basin is obvious,and changes in watershed land use have an impact on changes in soil erosion intensity,which are mainly manifested by the leading role of reduced forest land area on the growth of slightly and slightly eroded areas,grasslands The decrease in area is the main reason for the decrease in the area of extreme strength.The rapid increase in the area of bare land promotes the increase in the area of severe erosion.(3)From 2000 to 2017,the total soil erosion in the Koshi River Basin first increased from 1029.04×10~8t to 1071.19×10~8t,and then decreased to 746.611×10~8t.The areas with high values of soil retention intensity were concentrated in Sindhupalchok,Dolakha,Solukhumbu,Sankhuwasabha,Tapejung,Okhaldhunga in the mountainous areas of Nepal.Low-value areas are mainly distributed in Rautahat,Sarlahi,Mahottari,Dhanusa,Siraha,Saptari,and Sunsari in the Nepal Plain,Gamba County,Nyalam County,China County,the west of Tingri County and the east of Tinge County.During the 17 years,the soil retention and soil retention intensity in the study area increased first and then decreased with the elevation;as the slope continued to increase,the soil conservation amount decreased and then increased,and the soil retention intensity continued to increase.From 2000 to 2017,the soil holding capacity of forest land,grassland,and arable land was relatively strong.However,due to the reduction of the three areas,the soil holding capacity declined.It can be seen that the reduction of the area of woodland,grassland and arable land plays a leading role in reducing the area of high-value areas for soil conservation,indicating that the three are of great significance for water and soil conservation and ecological security in the Koshi River Basin. |
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