Spatial Fragmentation And Differentiation Of Major Cities In The Yangtze River Economic Belt And Its Influencing Factors

At present,China's cities are in a period of high-speed construction.The problem of urban spatial fragmentation affects the improvement of urban space quality.The specific manifestations are the dramatic changes in land use during the urbanization process and the highly fragmented urban landscape.The flow of various material flows in the city is blocked,and weakening of organic connection in cities.A large number of large-scale and single-function plots appear in the city,and the level of urban vitality decreases.This article discusses the problem of "urban spatial fragmentation".On the basis of summarizing the representations and theories of urban spatial fragmentation at home and abroad,through in-depth analysis of the connotation of this concept through three aspects of form,connection and function,the construction of 10 indicators in three dimensions measuring model of urban spatial fragmentation.Combined with the nine major capital cities and two municipalities in the Yangtze River Economic Belt,the landscape index method,spatial syntax and information entropy method were used to quantitatively measure the spatial differentiation characteristics of major cities in the Yangtze River Economic Belt in 2017.Finally,based on the results of urban spatial fragmentation,the main influencing factors of urban spatial fragmentation are discussed from three aspects: natural geographic factors,social economic factors and government policy factors,andcorresponding optimization strategies are proposed to provide new ideas for current urban space research to enrich the research achievements of urban geography.From the research results:(1)The fragmented results of the three dimensions of form,connection and function are significantly different.From the perspective of morphological dimensions,the upstream areas of Guiyang and Kunming have a higher degree of morphological fragmentation,and the Chengdu Capital has a lower degree of morphological fragmentation;from the perspective of connection dimensions,the upstream and midstream urban connections have a higher degree of fragmentation,such as Chongqing and Nanchang,the downstream cities have a lower degree of fragmentation;from the perspective of functional dimension,the upstream and midstream cities have a higher degree of fragmentation,such as Guiyang,Kunming,and Nanchang,while the downstream functions such as Shanghai and Nanjing have a lower fragmentation.(2)The 11 major cities in the Yangtze River Economic Zone have different levels of spatial fragmentation.Among them,Guiyang has the highest spatial fragmentation level,and Chengdu has the lowest spatial fragmentation level.From the perspective of spatial distribution,it shows a trend of high in upstream cities and low in downstream cities.Cluster analysis method is used to cluster its comprehensive fragmentation index,and urban spatial fragmentation is divided into four categories.In general,the first category is relatively high fragmentation cities,represented by Guiyang and Kunming.The second category is a relatively sub-high fragmentation type,represented by Nanchang,Wuhan,Changsha in the middle reaches of the Yangtze River Economic Belt,and Hefei in the lower reaches.The third category is relatively moderately fragmented cities,mainly megacities,including Shanghai,Hangzhou,Nanjing and Chongqing in the upper reaches of the Yangtze River Economic Belt;the fourth category is relatively low fragmented cities,including Chengdu.(3)In terms of influencing factors,physical geographic factors,socioeconomic factors,and government policy factors have an impact on each dimension and the level of comprehensive fragmentation,but the degree of influence is significantly different.The physical altitude factor has a significant impact on the morphological and comprehensive fragmentation levels,and the proportion of the secondary industry and the average housing area in the socio-economic factors have a more significant effect on the link and functional dimensions.According to the influencing factors and the results of urban fragmentation,combined with the current status of urban development and the types of urban fragmentation,a corresponding optimization strategy is proposed to promote sustainable urban development.