Research On The Evolution Of Spatial Correlation Structure Of Urbanization In The Yangtze River Delta And Its Driving Mechanism

With the continuous improvement of China's urbanization level,the flow of urbanization elements has changed from slow flow between urban and rural areas to rapid flow at the scale of urban agglomeration,and urban agglomeration has become the main form of urbanization.Urban agglomeration is a whole with a certain spatial structure formed by the interaction of many cities in a certain region,and its spatial structure depends on the related state formed by the flow of urbanization elements.The goal of regional integration in the advanced stage of urban agglomeration spatial structure development is highly consistent with the requirement of urbanization in pursuit of high-quality development.How to introduce the results of multi factor interaction in the process of urbanization development into the research of urban agglomeration spatial structure,and explore the driving mechanism in the process of Urban Agglomeration structure evolution,is an important starting point of this research.At present,the urbanization of Yangtze River Delta has reached a high level,and the spatial structure of urban agglomerations is in a critical period of development and integration.Facing the problems of regional integration and high-quality development of urban agglomerations,whether the internal organization development of urban agglomerations is orderly and whether the structure is reasonable or not is in urgent need of competition and cooperation development of multi center and multi circle organizational structure in urban agglomerations under the change of globalization and economic cycle pattern It is of great significance to explore the evolution process and law of urban agglomeration with Chinese characteristics.Based on the spatial interaction theory and complex network analysis,this paper analyzes the comprehensive level distribution pattern of urbanization in the Yangtze River Delta from the three factors of population,land and economy,and constructs the spatial correlation model of urbanization through the spatial distance,and analyzes the spatial relationship of the Yangtze River Delta from the node characteristics,network characteristics,community characteristics and restructuring process The main conclusions are as follows:(1)The spatial distribution of the comprehensive level of urbanization in the Yangtze River Delta is obviously hierarchical,and the evolution process of its spatial structure presents the characteristics of "unipolar independent development,multi-core competition and cooperation development,and peripheral continuous development".The comprehensive level of urbanization in the Yangtze River Delta region presents the characteristics of high rank scale distribution in time,the trend of normal distribution is obvious,the number of towns in the middle rank is more,and the development system of comprehensive level of urbanization is relatively stable and mature;the spatial distribution pattern is basically stable,and the East-West difference of the whole region is greater than the north-south direction,showing five grades,with the exception of Shanghai ranking the first In addition,other grades show obvious grade variability and spatial polarization characteristics.From the perspective of local characteristics,the comprehensive level of urbanization in the Yangtze River Delta presents spatial correlation,the trend of spatial agglomeration is constantly strengthening,and the spatial difference is gradually increasing;from the perspective of the collaborative growth relationship between each town and its neighboring towns,it has high spatial integration,most towns have not undergone obvious transition,and the path dependence of spatial collaborative growth is obvious,but the provinces with large gap within the province have obvious characteristics There are relatively strong instability and dynamic,and the provinces with small gap have relatively stable and static local spatial structure.(2)The spatial correlation intensity of urbanization in Yangtze River Delta is increasing,forming a multi-level and multi center nested network structure with Shanghai as the pole,Nanjing and Hangzhou as the core,Hefei,Suzhou and Ningbo as the center,other prefecture level cities as the landing points,and counties and cities as the basis.At the level of county and city,the cities and towns at different levels have great variability.On the whole,they form a circle distribution pattern with Shanghai as the center,and gradually get rid of the characteristics of "long tail distribution".The structural form of spatial correlation intensity of urbanization in Yangtze River Delta region presents the evolution characteristics from skeleton structure,rudiment appearance,development and perfection to maturity,and naturally forms the hierarchical structure of core layer,sub core layer,non core layer and peripheral layer with regularity.In the process of development,the radiation scope of Shanghai,Nanjing and Hangzhou breaks through the boundary of administrative region,and the whole region is divided into three regions However,Hefei,as an independent central city within the province,has a weak radiation and driving effect on other cities.(3)The spatial correlation structure of urbanization in the Yangtze River Delta region presents obvious characteristics of community cluster distribution,showing four development modes: homogeneous development mode,single center development mode,double center development mode and multi center development mode.There are eight communities in the Yangtze River Delta,namely,Hu Su Xi Chang community,Hang Yong community,Jin Yi community,Wenzhou community,Nanjing community,Hefei community,Xu Huai community and Yan Lian community.The communities are constantly divided and combined.This paper adopts the "bottom-up" division method,and merges them step by step with time as the evolution clue,so as to obtain the community weight of the overall structure of the Yangtze River Delta During the evolution process of the group,the evolution model of "two cores and multi centers","one pole and one core and multi centers" and "one pole and one pair and two cores and four centers" have been formed.The last model has remained stable since 2010.The evolution process of community structure is the result of competition and cooperation with surrounding cities and towns on the basis of their own development needs,which will provide important data reference value and practical significance for the study of urban agglomeration,metropolitan area and other regional forms.(4)The formation and development of urbanization spatial correlation structure in Yangtze River Delta is driven by the interaction of administration,market,industry and finance,and it is the most dependent on administrative power.The eight driving factors screened out in this paper show significant effects,among which the urban fixed asset investment,local fiscal expenditure,the proportion of the secondary industry and the tertiary industry play a key role in the evolution of the spatial correlation structure of urbanization in the Yangtze River Delta,and have spatial differences.The interactive explanatory power of each driving factor is higher than that of a single factor,and it increases with time,forming a two factor enhanced interaction type with administrative support factor as the interaction center and a nonlinear enhanced interaction type with industrial structure factor as the interaction center.The interaction effect of administrative and industrial factors with other factors is obvious.The interaction and coordinated development of multi-level and multi factor factors constitute the driving mechanism of the evolution of urbanization spatial correlation structure in Yangtze River Delta region.The driving factors and the change of correlation strength are twoway interactive relationship.The government is the important support to promote the urbanization spatial correlation strength,and the market force is becoming more and more important and dominating Financial capital is an important guarantee and supply for its good operation.In the future,with the "high quality" development requirements of urbanization construction in Yangtze River Delta,its driving mechanism will be more complex and multifaceted.(5)There are the following main problems in the evolution process of urbanization spatial correlation structure in Yangtze River Delta: the centrality fault trend of urban nodes is obvious,and the degree of discretization is large;the path dependence feature of spatial directivity of urbanization spatial correlation network is prominent;some community structures need to be optimized,and the sense of participation in regional integration needs to be improved.The main suggestions include: Deepening the understanding of the evolution law of regional urbanization spatial correlation structure;considering the layout and optimization of regional spatial structure from the perspective of spatial correlation;paying attention to the Marginal Towns and their development in the spatial layout;innovating the urbanization system and mechanism according to the time and local conditions;paying attention to the balance and fairness in the development of regional integration Improve the participation and benefit sharing of members.