| Urban heat island is not only the product of urbanization,but also one of the environmental problems hindering the further development of urbanization.The green space in the city,such as green space and water,has a cooling effect,which can effectively alleviate the urban heat island effect,but the phenomenon of fragmentation and isolation of green patches in the city is serious,and the distribution is uneven.However,it is not feasible to build a large area continuous green space in the city.Therefore,the construction of green space ecological network is beneficial to optimize the layout of green space in the city,enhance the connectivity between cooling patches,and alleviate the urban heat island effect as a whole.Changle has developed into the coastal new city of Fuzhou,and it has ushered in the development opportunity of urban space reconstruction under the policy.therefore,this paper takes Changle as the research object,aims to enhance the connectivity of urban cooling space,and constructs the urban green space ecological network,that is,“cooling network”Based on the Landsat data of 2000,2010 and 2020,this paper uses atmospheric correction method to deduce the land surface temperature of the study area,analyzes the evolution characteristics of urban heat island in the past two decades,The dynamic attitude and thermal contribution index were used to analyze the evolution and cooling relationship of land use.Secondly,through the analysis of landscape morphology pattern,combined with the cooling effect and connectivity analysis of patches,the cooling source is determined.The comprehensive resistance surface is constructed by using geographic detector and principal component analysis,on the basis of which the green space ecological cooling network of Changle is further constructed,and the key elements of the network are identified.Finally,the cooling network is optimized by adding source,constructing stepping stone patches and repairing fracture points,and the optimized cooling network is evaluated by current diagram and network structure index analysis.The main conclusions are as follows:(1)in the past two decades,with the continuous expansion of construction land in Changle,the problem of urban heat island has become increasingly prominent.The shape of the high temperature zone shows a"point-line-surface"expansion trend,and the proportion of the heat island area is increasing.In 2020,the heat island area accounts for38%,which is mainly distributed in the western and eastern coastal plain areas of the study area.Secondly,the dynamic attitude of comprehensive land use in the study area is 0.47%,and the overall change is slow.The change of single land use type shows difference,the maximum change rate of dynamic attitude of construction land is the fastest,which is 5.60%,followed by cultivated land,bare land,grassland,water and woodland;the contribution index of woodland and water is negative,which has cooling effect,cultivated land,bare land and construction land is positive,which has warming effect,and the grassland is uncertain.The order of heat contribution index is construction land,cultivated land,bare land,grassland,water,woodland.(2)The driving factors of urban heat island in the study area are land use,NDBI,NDVI,elevation,slope and night light index,and the weights of each factor are 0.20,0.12,0.18,0.21,0.18 and 0.11 respectively.The high value area of comprehensive resistance surface in the study area is mainly distributed in the concentrated areas of eastern coastal cities,especially in industrial areas and near airports.(3)the main cooling types in Changle are woodland and water,and the core cooling effect of the seven landscape structure types is the most prominent,with a cooling rate of 14.45%.Finally,eight cooling patches with the highest connectivity are selected as the cooling source,which are mainly distributed in the south and north of the study area,including the green space with better ecology and landscape.(4)In this paper,12 cooling corridors in the study area were constructed,4 corridors and 2 sources with the highest important grade in the study area,and 23 obstacles in the network were identified,with a total area of 374.33hm~2 and 68 pinch points,with a total area of176.59hm~2(5)in view of the shortcomings of the cooling network,21 new cooling sources in the study area,11 stepping stone patches and 49fracture points were identified,and 59 optimized cooling corridors were obtained.a"double-net,three-belt,multi-point"green cooling spatial structure is formed.After optimization,the current value of the network increases from 0.24 to 3.94,the closure index increases from 0.31 to 0.47,the line point rate increases from 2.67 to 3.69,and the connectivity index increases from 0.57 to 0.66,indicating that the stability and complexity of the network structure have been improved.the overall connectivity is enhanced. |
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