On The Evolution Mechanism Of The City Size Distribution Of Central Plains Urban Agglomeration

Urban agglomeration is the mainstream and trend of global urban development.It is also the main form of China's new urbanization.As an important organizational form for integrating regional resources and optimizing urban spatial layout,it can promote the coordinated development of large,medium and small cities and small towns' radiation action.The State Council issued the “Reply on the Development Plan of the Central Plains Urban Agglomeration” on December 30,2016,marking the Central Plains urban agglomeration among the seven national clusters.The Central Plains urban agglomeration is located in the national “two horizontal and three vertical” urbanization strategic pattern,the land bridge channel and the Beijing-Guangzhou channel intersection area,which has great development potential and is currently at a critical stage of upgrading and upgrading.In this context,the study on the scale distribution and evolution mechanism of the urban agglomerations of the Central Plains,and the focus and direction of its future development are of great significance for optimizing the urban scale distribution system and improving the comprehensive competitiveness of urban agglomerations.First,a static analysis of the urban size distribution of the Central Plains urban agglomeration.The urban population data of 30 prefecture-level and above cities in 2016 were selected to analyze its hierarchical structure visually.It was found that the scale structure of the urban agglomerations of the Central Plains presented an “olive type”,and the scale structure of the city showed faults.The development of small cities was insufficient and the scale was small.The number is low;using the first city size,the first city index,the coefficient of difference and other indicators to compare the Central Plains urban agglomeration with the middle reaches of the Yangtze River,it can be seen that the size gap between the high and low order cities of the Central Plains urban agglomeration is obvious,and the situation is uneven;From the three perspectives of scale,economic scale and spatial scale,the urban population,regional GDP and urban area are selected as their metrics,and the “order-scale” test is carried out to obtain the urban population of the Central Plains,whether it is population,economy or space.The dimension features are significant.Secondly,it analyzes the dynamic evolution and mechanism of the urban scale of the Central Plains urban agglomeration.Summarize the structural changes of the original urban agglomeration urban system in different historical stages;calculate the Gini coefficient,the first city index and other indicators,the results show that the Gini coefficient is stable in the "decline-rise-flat" trend,the first city index of the Central Plains urban agglomeration is generally fluctuating The rising trend indicates that Zhengzhou's agglomeration is strengthening;applying nuclear density estimation and Markov transfer matrix to present the dynamic transfer process of urban agglomeration structure,and discovering the probability of medium-sized cities moving to large cities in the process of urban transfer in different scales Higher,the probability of large cities shifting to megacities and megacities to megacities is low;finally,the “sequence-scale” rule is tested,the urban system of the Central Plains urban agglomeration is in line with the “order-scale” distribution,and the size of the first city The distribution has gradually increased,but as the first city,Zhengzhou needs to enhance its core competitiveness,thereby improving its ability to drive the surrounding small and medium-sized cities.Finally,aiming at the evolution characteristics of the present,combined with the process of space-time evolution,a theoretical explanatory framework "fishbone driving model" for analyzing the evolution mechanism of the original urban agglomeration is constructed.Finally,the optimization strategies and suggestions for the urban scale system are proposed.Promote the construction of Zhengzhou metropolitan area,develop and expand regional central cities;foster the development of modern small and medium-sized cities,plan to build characteristic small towns;improve the inter-city transportation network of urban agglomerations,and realize the coordinated integration of urban agglomerations.