Analysis Of Ecosystem Services And Their Trade-off Synergies In The Danjiangkou Reservoir Area

The Danjiangkou Reservoir is the water source of the South-to-North Water Diversion Project in China,and the frequent human activities in recent decades have exacerbated the ecological and environmental pressure around the reservoir,so it is important to study the changes of ecosystem services in the Danjiangkou Reservoir Area and their trade-offs and synergies to achieve a win-win situation between regional development and ecological protection.Based on the In VEST model,GIS spatial analysis,and geographic probes,the study analyzed the spatial and temporal changes of four ecosystem services and their trade-off synergies relationships in the Danjiangkou Reservoir Area,including carbon storage,water production,soil conservation and crop production,and detected the main impact factors of the four services based on five years:2000,2005,2010,2015 and 2018.Combined with hotspot analysis and K-mean cluster analysis,the clustering distribution characteristics of the ecosystem services in Danjiangkou Reservoir were identified,with a view to providing a scientific and theoretical basis for the optimization of ecosystem services in Danjiangkou Reservoir.The main conclusions are as follows.(1)During 2000-2018,forest land in the Danjiangkou Reservoir Area was the most widely distributed and occupied the largest proportion of the area,accounting for more than 60%of the total area of the reservoir area.Due to the implementation of ecological engineering policies and urbanization development,the conversion of various land use types in Danjiangkou Reservoir Area was frequent during 2000-2018,especially the conversion of arable land,forest land and grassland,and the conversion of arable land to construction land and water area were the most significant,with451.33 km~2of forest land converted to arable land,228.04 km~2of arable land converted to water area and 152.47 km~2of construction land.The area of forest land converted to farmland is 451.33 km~2,and the area of farmland converted to water and construction land is 228.04 km~2and 152.47 km~2respectively,while the distribution of water and construction land is expanding,and the distribution of grassland,farmland and forest land is decreasing to different degrees.(2)The changes of carbon storage service values in the Danjiangkou Reservoir Area for five years from 2000 to 2018 showed a decreasing trend,and the overall values of water production,soil conservation and crop production services showed an increasing trend.The high value areas of carbon storage and soil conservation during the study period were mainly distributed in the higher elevation areas in the northeast,west and southwest of the reservoir area,where woodland and grassland cover a wide area,and the low value areas were mainly distributed in the lower elevation areas in the eastern and central parts of the reservoir area,where the main land types were arable land,construction land and water.The spatial distribution of water production services roughly forms a distribution pattern of higher water production in the eastern and southern areas of the reservoir area and lower water production in the northern and western areas.Crop production are mainly in Xichuan County,which is a plain area at low altitude in the reservoir area,and the arable land area is relatively concentrated.The results of Geodetector analysis show that the changes of carbon storage services are mainly influenced by vegetation cover,and water production,soil conservation and crop production services are mainly influenced by climatic factors.(3)The carbon storage and soil conservation,water production and soil conservation services in the Danjiangkou Reservoir Area showed synergistic relationships for five years from 2000 to 2018,with a significant trade-off relationship between carbon storage and water production services dominating,followed by carbon storage and crop production,and a weak trade-off relationship between water production and crop production and soil conservation and crop production.The ecosystem service relationships in the reservoir area in all years were dominated by strong trade-offs with a wide distribution,and weak trade-offs were mainly located in low elevation areas,and the overall area of trade-offs and low synergistic relationships was larger and showed an increasing trend.In different slope zones,carbon storage and water production,crop production and carbon storage,water production and soil conservation services are mostly trade-offs,and carbon storage and soil conservation,water production and soil conservation services are synergistic relationships.Under different land use types,water production and crop production showed a trade-off relationship in forest land,a synergistic relationship in cropland and grassland.(4)The results of the hotspot analysis of carbon storage,water production,soil conservation and crop production services in the Danjiangkou Reservoir Area for five years from 2000-2018 showed that:The hotspots of carbon storage were concentrated in the central and western parts of the reservoir area and the distribution of hotspots was gradually reduced.The distribution of water production hotspots is roughly striped,and the spatial distribution of hotspots for soil conservation is more consistent,concentrated in the northeast,west and southwest high altitude areas of the reservoir area.Crop production hotspots were mainly distributed in Xichuan County in all years.The clustering results of ecosystem services show that the water-producing areas are located at low altitudes near the reservoir waters;the ecologically fragile areas are scattered and have low service levels;the crop production areas are located in the central part of the reservoir and should continue to strengthen the crop production function;the carbon sequestration storage areas are mainly located in the northeastern part of the reservoir and have relatively low levels of water production and crop production services;the ecological balance areas are mainly located at higher altitudes and have strong supply capacity for all ecosystem services.The ecological equilibrium zone is mainly located in the higher elevation area,and the supply capacity of all ecosystem services is strong.