| With the development of society and economy,the natural environment gets more pressure,leading to the degradation of ecosystem then the decline of human well-being.Ecosystem service(ES),as the key of natural environment and human welfare,has been the important topic of social sustainable development as well as the focus of scientific research.Many governmental institutions and organizations together with research institutions have carried out ES studies since Millennium Ecosystem Assessment(MA)in order to promote ES research from theory to actual management and decision.However,this development process is faced with a series of challenges,including how to explicitly define ES types,how to precisely quantify ES and mutual relationship among ESs,how to analyze drivers and effects,particularly at various regional scale.Therefore,it is necessary to develop ES integration framework according to different regions and solve the key issues so as to apply ES theory to management.Watershed is the intensive interaction region of physical process and human activity,and suffers from emergency issues,such as water quality degradation,water shortage,sediment erosion,of which non-point source pollution(NSP)is the primary problem in water regulation,especially in eastern China.Therefore,considering key issues of most watersheds,we should promote ES study in these regions to optimize the mode of water environmental management.Based on the purpose of management and decision,we developed ES integration framework and analyzed key points in the framework as well as related domestic and international researches.We selected Jiangsu part of Tai Lake Basin as our study area due to its ecological and economic significance in China,and built ES classification system of the watershed to identify five critical services types(i.e.nitrogen and phosphorous purifications,water supply,soil retention and crop production)related to NSP.Then we used spatially explicit models and empirical estimations to quantify and map indicators of ESs.GIS,geostatistical method and statistical analysis were applied to assess ES spatial and temporal multi-scale characteristics,containing single ES and relationship of multiple ESs.Driver mechanisms of multiple ESs were analyzed based on factors quantification,then land use and climate change were predicted to analyze ESs effects at different scenarios.Finally,in accordance with these results,we provided related policy implications,focusing on the spatial scale of managing NSP in the rural areas,measures of optimizing nitrogen and phosphorous services simultaneously,and water management in the development of urbanization.Our main conclusions and related suggestions were as follows.(1)We summarized the challenges of ES application in the practice,and developed ES integration framework with the key points of classification,quantification,assessment and drivers.The structure of the framework is similar to driver-state-response model,which integrates key points and approaches to clear ES research routes.As the first point of framework,ES classification was illustrated in details to build classification system suitable for watershed water management.There were 3 grades(section,group and type)in our classification system with categories of direct services,indirect services and benefit.In our case study,considering water managing demand and data availability,we selected nitrogen and phosphorous purification as direct services(with the inverse proxies of nitrogen and phosphorous loadings),water supply and soil retention as indirect services,and crop production as benefits,Secondly,we reviewed on the literature of ES quantitative methods,spatial and temporal scale analysis of one ES and their relationship,along with scale effect,then explained these corresponding contents in our study.Similarly,based on literature reviews of ES drivers,we chose 31 environmental and socio-economic factors in study area,and introduced their characteristics as well as influence mechanisms to lay the foundation for the case study.(2)The results of ESs spatial features in 2010 indicated that in the whole region there were different spatial distribution features of every ES,however,in First-class Conservation Zone around Tai lake,direct and indirect services tended to reduce as the increasing distance from the lake.Factorial kriging analysis(FKA)divided ESs into 2 spatial component,the small scale of 12 km and large scale of 83 km.At 12 km scale,ESs showed the obvious spatial heterogeneity while they had the homogenous distribution at 83 km,which explained the scale-dependent of ESs.The relationship of ESs further verified scale effect,as the result of higher correlation with the scale rise.Social-economic factors and physical environment factors influenced spatial variability of the small scale and large scale,respectively.ESs with higher spatial relationship were determined by similar factors.For instance,both NL and CP were distinctly influenced by vegetation land and agricultural activities,leading to the high coefficients between them.(3)In temporal scale,there were different changing processes of every ES from 2000 to 2010.Nitrogen loading(NL)and phosphorus loading(PL)were taken as the examples.As the aspect of total amount,NL increased before falling slightly,and PL had an increasing trend;as the aspect of changing distribution pattern,they both mainly showed the weak increased area.Among county level administration,NL in Suzhou urban area and Kunshan obviously decreased while Liyang,Yixing and Danyang increased;PL of Suzhou and Wuxi urban area increased distinctly.Although NL and PL were both negative influenced by climatic and hydrological factors,their positive factors were different;rural residential area and arable land were the main positive drivers of NL,while the density of urban construction land had a positive impact on PL.There were synergy and tradeoff of ES relationship in the temporal scale,above all,the synergy of NL and crop production(CP),NL and water supply(WS),NL and PL,the tradeoff of PL and CP.The spatial patterns of these relationships were embodied in the form of both positive changed area,both negative area and opposite changed area.The drivers of ES relationship in temporal scale were intricate,such as NDVI promoted the relationship of NL and CP with the occurrence probability was 8.744,but negatively affected NL and WS at probability of 0.244.(4)Under the impact of land use change,NL,PL and CP responded distinctly,and PL increased 4.02%,NL and CP reduced 8.64%and 24.13%,respectively.Climate change in 2011?2100 would negative impact these five ESs,of which CP had the most obvious change and would decline rapidly in the RCP 8.5 scenario,while NL and PL increased less.Under influence of land use and climate change,NL would decrease around 8.5%,PL would increase 4.2%,WS,SR and CP had the different reduction.ES relationship in 2011?2100 indicated the synergy of NL and CP would fall off,and tradeoff of NL and PL would also tend to weak.(5)We provided three policy implications based on our results.At the aspect of managing rural NSP,some measures(such as farmland fertilization,rural land circulation,returning the grain plots to forestry or wetland,etc.)should implement at 12 km scale to effectively improve ecosystem structure and process couple with promoting its water quality function.While measures should be seriously schemed in protection of other services at 83 km.Moreover,NSP management should be carried out at the administrative scales of town and municipality in order to match ecological scale of ESs supply and social scale of management as possible.At the aspect of optimizing nitrogen and phosphorous services,the result of spatial features analysis suggested that at large scale water quality services could be improved simultaneously by regulation measures of land use and climate adaptation.At small scale,different policies should be implemented to manage nitrogen and phosphorus respectively.Policies related to crop planting and rural environment regulation should be designed to improve nitrogen service,while urban development planning and basic facility construction to improve phosphorus service.Driving force in the temporal scale further verified the feasibility of collaborative management(such as increasing vegetation cover and improving soil structure)and necessity of diverse management(such as optimizing the production and living behavior of farmer and citizen respectively).At the aspect of water management in the development of urbanization,regional governor should pay more attention to phosphorus pollution.Meanwhile,landscape units should be arranged rationally to mitigate urban surface runoff and intercept nutrients.During the construction of urban agglomeration,in order to ensure ecosystem health,governor should consider ecological security pattern by designing landscape patch,reen corridor,ecological network,etc.In addition,construction land expansion might occupy arable land,and the relationship of crop production,water quality services along with water supply should be coordinated to promote the progresses of urban and rural areas as a whole. |
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