Study On The Optimization Of Blue-Green Space In Wuhan City Based On Connectivity

Urban blue-green space plays an important role in maintaining urban ecological balance,enhancing natural environmental capacity and improving ecological environment.Rapid urbanization has led to accelerated land use change,encroachment on blue-green space,fragmentation of ecological land,and consequent degradation of urban ecosystem functions.Related studies have shown that reduced connectivity is a direct driver of ecosystem function degradation,impeding the flow of certain ecological processes between natural resource patches.However,in urban planning,ecological nodes that play a key role in the connectivity of blue-green spaces are often neglected.In this study,we analyzed the evolution characteristics of blue-green space and landscape pattern from 2000 to 2020 in Wuhan city,and based on the framework of"ecological source extraction-resistance surface construction-ecological corridor simulation-strategic node optimization".--The ecological security pattern is constructed based on the framework of"ecological source extraction-resistance surface construction-ecological corridor simulation-strategic node optimization",and the important strategic nodes are identified for protection and improvement to promote effective territorial spatial planning and enhance regional connectivity in Wuhan.The main conclusions are as follows(1)Between 2000 and 2020,the blue-green space in Wuhan decreased from8269.26 km~2to 7019.63 km~2,mainly caused by urban expansion,and each blue-green space factor showed a trend of"one decrease and three increases",among which arable land decreased by 1557.61 km~2,while forest land,grassland,water bodies,increased by 108.52 km~2,108.52 km~2,108.52 km~2,and 108.52 km~2,respectively.The transformation between cropland and forest land is the most obvious,with 460.10 km~2of cropland to forest land and 272.13 km~2of forest land to cropland.(2)At the type level,the maximum patch index(LPI)value of cropland was the dominant type in the study area,and the LPI values of grassland were all less than0.001 with the lowest dominance.The dominance of blue-green space in the whole study area decreased during the study period,and the number of patches(NP)and patch density(PD)values of each blue-green space factor increased,and the average patch area(AREA＿MN),cohesiveness index(COHESION)values decreased,indicating that the fragmentation of each patch deepened and connectivity decreased;the spreading index(CONTAG)and aggregation index(AI)values decreased period by period,and the Shannon evenness index(SHEI)and Shannon diversity index(SHDI)values increased slightly,indicating that the landscape diversity of the study area increased but the landscape integrity decreased.(3)At the municipal scale,the core area decreased sharply from 7,776.85 km~2to3,901.18 km~2from 2000 to 2020,and the fragmentation of the core area patches deepened;at the ringline scale,the fragmentation of the core area in the outer ring was the most significant,with an area reduction of 2,780.87 km~2.Based on the core areas obtained from the Morphological Spatial Pattern Analysis(MSPA)landscape classification,10 ecological source areas(class block importance d PC>1)were selected through area screening,connectivity evaluation and importance evaluation,mainly in the northwest,southeast and northeast of Wuhan.(4)The selection of resistance factors included four aspects of land use,topography,human interference and ecological protection,and each resistance factor was divided into six classes,and the single resistance factor values were obtained by combining the characteristics of the study area and related studies,and the weights of each resistance factor were 0.387,0.316,0.109 and 0.188 respectively by using hierarchical analysis,and weighted by Arc GIS to obtain The integrated ecological resistance value is spatially characterized as"high in the middle and low around".(5)Based on the minimum cumulative resistance model(MCR),45 ecological corridors were identified,totaling 2426.70 km,with an ecological network closure index(αindex)of 0.39,an ecological network connectivity index(βindex)of 1.67,and an ecological network connectivity index(γindex)of 0.60.12 first-grade corridors with a force greater than 15 were screened by the gravity model;based on Linkage Mapper identified 21 ecological corridors,totaling 1223.72km,with the ecological network structure indexαindex 0.43,βindex 1.62,γindex 0.64,and the gravity model screened a total of 8 primary corridors with a force greater than 15.In summary,the final ecological network was obtained by screening and de-weighting,and the Linkage Mapper tool was used to identify 548 ecological pinch points with a total area of 2.7801km~2and 473 obstacle points with a total area of 8.874km~2,and the top ten ecological nodes and ecological obstacle point areas in terms of area were extracted as key strategic nodes for improvement and protection,respectively.