Analysis Of Ecosystem Service Trade-offs And Supply-demand Balance In Karst Area Of Southwest China

As an important bridge and link between the natural environment and human well-being,ecosystem services have great significance for the rational allocation and utilization of natural resources.The ecosystem can provide multiple services,and there are complex trade-offs and synergies between ecosystem services.Human beings are often faced with the choice of ecosystem service supply under the dual impacts of interest driven and inner real demand,and intentionally or unintentionally weaken the supply of other types of ecosystem services.On the contrary,the decline of the supply capacity of ecosystem services will also aggravate the contradiction between the supply and demand of regional ecosystem services,which will affect the sustainable development of the region.Therefore,the relationship between ecosystem services and human well-being can be more effectively revealed only by comprehensively considering trade-offs and synergies of ecosystem services supply and human demand for services,and scientifically understanding the whole process of ecosystem services from generation,delivery to use.Based on three ecological models of In VEST,RUSLE,and CASA,combined with multi-source data such as land use,NDVI,DEM,and meteorological observations,three key ecosystem services are accurately calculated in the Karst area of Southwest China from 1982 to 2015,including water yield,soil conservation,and net primary production(NPP).And the correlation analysis and spatial hotspot mapping are used to analyze the spatio-temporal characteristics of ecosystem service trade-offs and synergies at regional and provincial scales.The demand of three kinds of services is calculated by using social and economic statistics,and the balance between supply and demand of ecosystem services in the region is analyzed and evaluated.Finally,the service flow delivery path is drawn and the service flow is quantified.The main conclusions are as follows:(1)During 2000-2015,soil conservation,water yield,and NPP showed an increasing trend in Karst area,with annual growth rates of 19.97 t/(hm~2·yr)、3.37 mm/yr、3.69 gc/(m~2·yr),respectively.The spatial distribution pattern of soil conservation was similar in the past 16 years.The high-value areas(>5000t/(hm~2·yr))were mainly distributed in western Sichuan,western Yunnan,western Hubei,eastern Chongqing,and Guangdong.The spatio-temporal pattern of water yield changed significantly.In 2000,the low-value areas(<-300 mm)of water yield were mainly distributed in western Guangdong and southeastern Guangxi,but in 2015,these areas turned into high-value(>900 mm).NPP increased from north to south,and the high-value(>1100 gc/(m~2·yr))were mainly distributed in Southwest Yunnan and Guangdong.(2)The multi-year average of ecosystem services in Karst area presented as synergies both between water yield and soil conservation and that between water yield and NPP,the correlation coefficients were0.146 and 0.143,respectively.But the interaction between water yield and NPP was prone to trade-offs,the correlation coefficients were-0.157.The synergies between soil conservation and water yield showed a trend of strengthening and then weakening in the past 16 years.In most years,there was significant trade-offs between water yield and NPP.The synergies between soil conservation and NPP gradually strengthened from 2000 to 2007,and the synergies showed a trend of weakening and then strengthening in2007-2015.(3)There existed obvious spatial heterogeneity in the interaction between trade-offs and synergies.Specifically,the interaction between NPP and soil conservation was significantly different from the east and west.There were mainly trade-offs in the eastern study area,while synergies in the western study area.The interaction between NPP and water yield was mainly represented as trade-offs in the western and northeastern study area,while synergies in the middle and southeastern study area.The synergy between soil conservation and water yield was widely distributed,accounting for 90.01%of the total study area.(4)The demand for soil conservation fluctuated and increased,the demand for water increased firstly and then decreased,and the demand for carbon sequestration continued to increase.High-value areas of soil conservation demand(>800 t/(hm~2·yr))were mainly distributed in western Sichuan,western Yunnan,and Chongqing.High-value areas of water demand(>2.5×10~5m~3/(km~2·yr))were mainly distributed in southeastern Guangdong,eastern Hubei,eastern Hunan,and central Guangxi.In 2000,high-value areas of carbon demand(>500 t/(km~2·yr))were relatively rare.But in 2015,most areas became high-value areas,such as eastern Sichuan,Guangdong,eastern and central Hunan,eastern Hubei,and western Chongqing.(5)The high level soil conservation service flow was mainly distributed in the Nujiang,Lancang,Jinsha,and Heishui River Basin in Yunnan,and the Yalong,Dadu,and Minjiang River Basin in Sichuan,while the low level service flow was mainly distributed in the Nanpan River Basin in Yunnan.The low level water yield service flow was mainly distributed in the Pudu and Niulan River Basin in Yunnan.The high level carbon sequestration service flow mainly appeared in Southwestern Yunnan,and most regions’lower service flow was transformed into medium level service flow in 2015.