Spatial Structure Characteristics And Optimization Of Urban Agglomeration In The Middle Reaches Of Yangtze River

The urban agglomeration is based on one or several mega cities as the core,and is distributed along a certain traffic axis.The urban agglomerations are composed of cities of different functions and sizes.With the increase of economic globalization and urbanization level,urban agglomerations,as the economic center of a country and a region,have become the core geographic units participating in the international division of labor and cooperation.The urban agglomeration in the middle reaches of the Yangtze River,as a large-scale urban agglomeration,is playing an important role in advancing China’s strategy for developing the Yangtze River Economic Belt and promoting the rise of Central China.According to the evolution rules of urban agglomerations,urban agglomerations in the middle reaches of the Yangtze River can be divided into three stages: budding,starting,and expanding.The urban spatial structure evolution model includes the polar nuclear structure of the Wuhan metropolitan area,the Changjiu dual-core structure,and the Changyue dual-core structure.Core-edge analysis was conducted in Wuhan,Changsha,and Nanchang metropolitan areas.In 1995,2005,and 2015,the core areas of the three core metropolitan areas in the middle reaches of the Yangtze River gradually expanded,and the marginal areas expanded from the suburbs of cities to surrounding counties and cities.The sub-central city of the area.The urban quality evaluation results of urban agglomerations in the middle reaches of the Yangtze River indicate that from 2000 to 2014,the comprehensive strength of the urban agglomerations in the middle reaches of the Yangtze River can be divided into three levels.Among them,Wuhan is the first level,Changsha and Nanchang are the second level,and the remaining cities are the third level..The strength of the city attractiveness weighted by the spatial interaction strength indicates that in 2000,2006,2010,and 2014,the core of gravity in the middle reaches of the Yangtze River was changed from singlecore Wuhan to three cores of Wuhan,Changsha,and Nanchang,and sub-centers are forming..The calculation results of the fracture point indicate that the core areas of attraction in Wuhan Metropolitan Area include Jingmen,Ezhou,Xiaogan and Huangshi.The core areas of attraction in Changsha metropolitan area are Yueyang,Changde,Yiyang,Loudi and Xiangtan.The core attraction areas of Nanchang metropolitan area include Jiujiang and Shangrao.Fuzhou,Xinyu.The order-scale results show that the urban system of the urban agglomeration in the middle reaches of the Yangtze River presents a median distribution pattern.The urban agglomeration generally lacks super mega cities and super mega cities,and the gaps between the low tier cities are relatively large.The fractal geometry method was used to calculate the geometric spatial structure of urban agglomerations in the middle reaches of the Yangtze River.It was found that Wuhan,Changsha,and Nanchang have good optimization characteristics in the geometric space as the core cities of the middle reaches of the Yangtze River.At the same time,urban agglomerations in the middle reaches of the Yangtze River have spatially focused characteristics around rivers and traffic trunks,which provide support for advancing the development of the urban agglomerations with a point-and-belt line and a line-to-face approach.In order to achieve the coordinated development of the urban clusters in the middle reaches of the Yangtze River,we must adhere to the three core growth poles of Wuhan,Changsha,and Nanchang,promote optimal adjustment of the industrial structure within the urban agglomeration,strengthen the construction of comprehensive urban transportation networks,and strengthen open cooperation within and outside urban agglomerations.Optimize the city’s urban construction in the city center.