Spatio-temporal Differentiations And Driving Forces Of Ecosystem Services And Urban Expansion Simulation With Constraints Of Them

As an indicator to measure the importance of ecological structure and function,ecosystem services(ESs)can be utilized to guide urban planning and ecological protection.It is reported that ESs in China are being deteriorated due to the rapid urban land expansion and human activities enhancement.In turn,such degradation would damage human production and living conditions,directly or indirectly threatening sustainablile socio-economical development and human well-being.On the basis of current researches,this study analyzed the spatiotemporal differentiations of multiple ESs and trade-offs between them,explored the driving forces of ESs under the effect of spatial dependence,and carried out multi-scenario simulations of urban expansion under ESs constraints.This study took Wuhan as the study area to apply the proposed methods,with aim to provide theoretical and methodological supports for the green development of Wuhan.The specific conclusions are as follows:(1)Spatiotemporal differentiations of ecosystem services on multi dimensions and trade-off between themSix types of ESs were selected and evaluated,they were:grain production(GP),water yield(WY),carbon storage(CS),biodiversity conservation(BC),erosion prevention(EP),and outdoor recreation(OR).On this basis,the multi-dimensional spatial differentiations of ESs(and their changes),such as quadrant differentiation,urban-rural gradient differentiation,administrative differentiation,urban function differentiation,were analyzed.Finally,trade-offs between the multiple ESs were analyzed.The results showed that:(1)Spatial patterns of six ESs in Wuhan showed obvious spatial heterogeneity,and those on different time nodes featured"overall similarity and local difference";(2)Except for WY and EP,other ESs featured obvious"quadrant differentiation";(3)All ESs showed“gradual change”along with urban-rural gradient;(4)Except for CS and BC,other ESs featured obvious"administrative differentiation";(5)All ESs showed the characteristics of"monotonous change"along with functional divisions;(6)There were obvious trade-offs or synergies between multiple ESs.At different time nodes,relationships between multiple ESs showed characteristic of"overall similarity and local difference".The evolution of relationships between multiple ESs was affected by the change of climate,land use,vegetation cover and other factors.(2)Analysis on the driving forces of ecosystem services with consideration of spatial dependenceComing from four aspects of"topography-climate-socio-economy-land use/land cover",driving factors of ESs were selected.Collinearity and correlation tests were implemented to determine the effective factors.Moran’s I method was utilized to diagnose the spatial dependence of ESs.Spatial regression model(SRM)was implemented to explore the influences of these factors,and the"leading factor","key factor"and"main factor"for ESs bundles were identified.Finally,the model performace between SRM and ordinary least square(OLS)was compared.The results showed that:(1)“Clustering characteristics”existed in the spatial distributions of six ESs;(2)The spatial lag model was more suitable for the regression of GP,CS,BC and EP,while the spatial error model was more suitable for the regression of WY and OR;(3)The impacts of these environmental indicators on ESs bundles were different;(4)The“leading factors”affecting ESs bundles were forest land area proportion,cultivated land area proportion,forest land aggregation degree and water area aggregation degree;the“key factors”were elevation,construction land area proportion,construction land average perimeter area ratio,cultivated land average perimeter area ratio and water area average perimeter area ratio which affect ecosystem service cluster;the“main factors”were slope,distance from road,POI density,average perimeter area ratio of landscape,average perimeter area ratio of forest land,aggregation degree of cultivated land and aggregation degree of construction land;(5)Spatial regression model had advantage in regressing ESs with their driving factors.Except for WY,the goodness of fits of SRMs for other ESs were higher than 0.75.R ~2and log likelihood of SRMs were higher than the corresponding parameters of OLSs,while AIC and SC were lower than those of OLSs.(3)Simulation of urban expansion based on constraints of ecosystem services and their trade-off relationshipsOrdered weighted average(OWA)was firstly utlized to aggregate the multiple ESs,and the risk and trade-off values during the aggregation,which vary with differentβ,were quantified.A combined model of Markov,BPANN,OWA and CA was then constructed to simulate urban expansion based on ecological constraints.After trained and validated,the combined model was utilized to predict future urban land patterns.Different ecological constraint scenarios were designed by varying theβparameters of OWA,and urban expansion schemes under the four scenarios were generated.The quantity structure,spatial layout,landscape patterns and ecological effects of these urban expansion schemes,were compared and analyzed,to provide the basis for the formulation of eco-friendly urban planning.The results showed that:(1)The comprehensive value of ESs,as well as risk effect and trade-off relationship during aggregation varied with theβparameter of OWA;(2)The combined model of Markov,BPANN,OWA and CAcould effectively predict the quantity and spatial distribution of expanded urban land.The accuracy of Makov chain,BPANN and OWA-CA models were more than 95%,95.241%and 0.824,respectively;(3)Wuhan planners in the past period of time adopted the strategy of"protecting superior ecosystem service",which only payed attention to the particular ecosystem service with highest value.This strategy produced the smallest trade-off effect between multiple ESs,but may cause greater ecological protection risks;(4)In different ecological constraint scenarios,the spatial distributions of urban land in Wuhan in 2025 were different.Compared with the weak constraint scenarios(β>1),the urban expansion rates were lower in urban surrounding areas with good ecological conditions,but higher in the areas with strong construction and population intensities,in the strong constraint scenarios(β<1);(5)Among the four typical eco-constaint scenarios,the"protecting dominant ecological service"scenario is the most beneficial to tap the potential inward city and protect the green space around the city.As well,it will not cause the excessive fragmentation and irregularity of urban land patchs,which is superious to the traditional"protecting dominant ecosystem service"scenario.(4)Optimization of urban expansion based on bi-level ecological constraints of regional ecological carrying capacity and local ecosystem servicesThe regional ecological carrying capacity was combined with the local-level ecosystem services to build a bi-level ecological constraint hierarchy of urban expansion simulation.The urban expansion was carried out by using the combined model of Markov,binary logistic(BLR)and CA.In the process of model prediction,the global level of regional ecological carrying capacity was used to modify the"conversion threshold"of CA model,while the local-level ecological importance index was used to modify the"conversion probability"of CA.By introducing different levels of ecological constraints,urban expansion simulations at multiple scenarios were implemented.Spatial distributions,ecological loss effects,quantitative characteristics of urban land under different scenarios were compared,so as to provide various alternative strategies for urban expansion in Wuhan.The results showed that:(1)The Markov-BLR-CA model was effective to conduct urban expansion simulation,with prediction accuracy being 81%;(2)The spatial dislocation of ecological carrying capacity and ecological importance existed in Wuhan,and the integration of double-layer ecological constraints was expected to coordinate urban expansion and ecological protection on multiple levels;(3)Under four different ecological constraints(namely BAU,GEC-UES,LEC-UES and GLEC-UES),the spatial distribution of urban land in 2025 showed that considering bi-level ecological constraints would help to promote the coordination of urbanization with regional ecological balance and local ecosystem services;(4)In the two scenarios with global ecological constraints(i.e.,GEC-UES and GLEC-UES),the distribution of new urban land existed more in areas with higher ECC value(such as Jiangxia District and Caidian District)would increase.In the two scenarios with local ecological constraints(LES-UES and GLEC-UES),urban expansion would occupy less arable land and water;(5)Considering global and local ecological constraints would be beneficial to promote compact and filling urban development,and avoid decentralized expansion.