Spatial And Temporal Evolution Of Ecosystem Services And Its Trade-offs And Synergies In Ningxia Hui Autonomous Region

Ecosystem services are the basis of survival and development for human,which maintain human society and natural environment.Its decline has a direct impact on regional ecological security,resulting in a series of social problems.Ningxia Hui Autonomous Region is an important part of the ecological security barrier on the Loess Plateau.Its ecological status is important,but its ecological environment is sensitive and fragile,and the phenomena of desertification and soil erosion are serious.Therefore,exploring the temporal and spatial change pattern of ecosystem services and the trade-off or synergy between ecosystem services,and considering ecosystem service management in the process of policy-making is an effective way to promote socio-economic development and protect the ecological environment.Taking Ningxia as the study area,this paper quantitatively evaluates the water supply service,soil conservation service,carbon fixation service and wind prevention and sand fixation service in Ningxia,and analyzes its temporal and spatial change pattern;Then use correlation analysis to analyze the trade-off or synergy of ecosystem services from grid scale,county scale and land cover type scale,and explore the trade-off and synergy of ecosystem services at different scales.The main results of the study are as follows:（1）From 2000 to 2015,the service volume per unit area of water supply services in Ningxia was 53.85mm,47.76mm,75.03mm and 80.58mm respectively,and the water supply services showed an upward trend as a whole.From 2000 to 2015,the service volume per unit area of soil conservation services in Ningxia was 24.16kg·m^-2·a^-1、18.88kg·m^-2·a^-1、21.94kg·m^-2·a^-1 and 18.53kg·m^-2·a^-1 respectively.The overall trend of soil conservation services was downward.The soil conservation rate shows a gradual upward trend,indicating that the function of soil and water conservation in Ningxia has improved year by year.From 2000 to 2015,the service volume per unit area of carbon sequestration services in Ningxia were 348.84g·m^-2·a^-1、442.67g·m^-2·a^-1、570.47g·m^-2·a^-1 and 593.58g·m^-2·a^-1 respectively.Vegetation carbon sequestration services showed a gradual upward trend.From 2000 to 2015,the service volume per unit area of wind prevention and sand fixation services in Ningxia was 1.11kg·m^-2·a^-1、0.1kg·m^-2·a^-1、0.39kg·m^-2·a^-1和0.11kg·m^-2·a^-1,the overall service of wind prevention showed a downward trend.The retention rate of sand fixation is a gradual upward trend,indicating that the current situation of windbreak and sand fixation function in Ningxia is improving year by year.（2）The high value area of water supply service is mainly located in the southern mountainous area,and the low value area is mainly located in the northern irrigation area.There is an obvious gradient difference in water supply service from south to north.Forest land and grassland are the main sources of water supply services in Ningxia.The high value areas of soil conservation services are mainly located in the southern mountain and the northern Helan Mountain,and the low value areas are mainly located in the central arid area and the southern mountain.The overall trend of soil conservation services is decreasing from south to north.Forest land and grassland are the main sources of soil conservation services in Ningxia.The high value area of vegetation carbon sequestration is mainly located in Liupan Mountain in the South and Helan Mountain in the northwest,and the low value area is mainly located in the central arid area.Forest land and grassland are the main sources of vegetation carbon sequestration services in Ningxia.The high value area of wind prevention and sand fixation service is mainly located in the central arid zone,and the low value area is mainly located in the southern mountainous area and Yinchuan Plain of Ningxia.（3）On the grid scale,water supply services and carbon sequestration services show a significant synergistic relationship as a whole,water supply services and soil conservation services show a significant synergistic relationship as a whole,carbon sequestration services and soil conservation services show a significant synergistic relationship as a whole,and carbon sequestration services and windbreak and sand fixation services show a slightly significant trade-off relationship as a whole.At the county level,water supply services and carbon sequestration services show a very significant synergistic relationship,water supply services and soil conservation services show a very significant synergistic relationship,carbon sequestration services and soil conservation services show a very significant synergistic relationship,and the correlation coefficients show a trend of increasing first and then decreasing.On the scale of land use types,water supply services and carbon sequestration services show a significant synergistic relationship,water supply services and soil conservation services show a very significant synergistic relationship,carbon sequestration services and soil conservation services show a significant synergistic relationship.（4）Due to the trade-offs between different ecosystem services,the collaborative relationship will produce spatial differences with spatial distribution,and fluctuate with time.This means that when formulating and implementing ecological protection policies,we need to adjust measures to local conditions,consider the spatial differences of trade-offs and synergies between different ecosystem services,and implement different zoning policies.