Research On The Phenomenon And Formation Mechanism Of The Shrinking Urban Area Of ??Chengdu-Chongqing Urban Agglomeration

The phenomenon of "urban shrinkage" and its Chinese characteristics is one of the key areas of concern for urban geography and urban and rural planning in recent years.At present,domestic researches on shrinking cities focus on the middle and late urbanized areas such as Northeast China and the Pearl River Delta region.Some researches have also found that local shrinkage caused by population migration,such as “Hollow Village” and “Hollow Town”,which occurred in underdeveloped areas.These urban shrinking cities are represented by “the Sichuan-Yunnan-Guizhou Linkage Area” and “Southwest Zhejiang-Western Fujian Linkage Area”.However,existing researches lack accurate description and judgment of the significant urban shrinkage phenomenon exising in key development areas,which identified by spatial strategic planning and main functional area planning.The chengdu-chongqing urban agglomeration,a state-level urban agglomeration leading the development and opening up of the western region,is taken as the research object to describe the spatial distribution pattern and spatial structure characteristics of the shrinking cities in the region accompanied by the urbanization process.141 districts(cities)and counties in chengcheng-chongqing urban agglomeration were selected as research samples to analyze the resident population data in the recent decade(2009-2018),measure the degree of population contraction in this region,and describe its spatial pattern.Research findings:(1)according to the official demographic data,in the urban agglomeration of chengdu-chongqing in recent ten years,the resident population generally increased,but the population outflow trend is still significant,there are 30 districts(cities)and counties can be clearly diagnosed with the phenomenon of urban contraction,accounting for 21.1% of the total sample number.The 30 shrinking cities lost about 1.0611 million people in total.The counties with the largest population loss(renshou county,meishan city)had 135,800 people,while the counties with the smallest population loss(wutongqiao district,leshan city)had 10,600 people,with a median population loss of 24,000 people.(2)the average population growth rate of the shrinking cities is-6.3%,among which the population growth rate of the districts and counties with the most serious population loss is-10.55%.In comparison,the average population growth rate of the remaining unshrinking areas in the urban agglomeration is 8.1%.(3)input the contraction index of each sample for the measurement of global spatial autocorrelation(Moran I)and local spatial autocorrelation(LISA)index.According to the results of Moran I index and LISA clustering characteristics,the shrinking cities of chengdu-chongqing urban agglomeration are not randomly distributed,but show obvious spatial aggregation.(4)regional agglomeration characteristics of shrinking cities in spatial distribution were investigated.The most significant shrinking areas were concentrated in southern sichuan,with 15 districts and counties concentrically contracting.The convergence and contraction area of 5 districts and counties appeared in the boundary area between chengde and Germany.In northeast chongqing,there are four districts and counties concentric contraction.The confluence of sichuan,chongqing and guizhou has appeared in three districts and counties.(5)according to the spatial structure proposed in the chengdu-chongqing urban agglomeration development plan,the location type of the contraction region can be judged,which can be divided into five types: the edge contraction type of urban agglomeration,the inner contraction type of metropolitan circle,the outer contraction type of urban belt,the inner contraction type of urban compact area,and the central contraction type of the main axis of chengdu-chongqing development.The research further finds that the regional agglomeration of the above shrinking cities is accompanied by the region's lower level of economic development and administrative level,as well as the unbalanced and inadequate space,population and economic characteristics of regional development.Based on this,the formation mechanism framework of "regional factor flow pattern--drivers of shrinking regions" is constructed,and the formation mechanism of the phenomenon of shrinking urban agglomeration is judged as follows:(1)from the perspective of the flow of resource elements in urban agglomeration,the flow of resource elements has a direct impact on the regional agglomeration of shrinking cities through the action mechanism of spatial "correlation" and "agglomeration";(2)the characteristics of factor flow pattern are closely related to the driving factors of regional economy,society,ecology and facilities;(3)in the relationship between the action mechanism of factor flow and driving factors,the "correlation" mechanism is directly related to "facility factor" and "ecological factor",and the "agglomeration" mechanism is directly related to "economic factor" and "social factor";(4)focus on the agglomeration and contraction region.The driving force of the contraction region is closely related to the regional economic development direction,urban administrative level,industrial layout infrastructure,infrastructure construction conditions,regional natural resources and environment and other factors;(5)the main driving factors of agglomeration and contraction regions are different,and the degree of contraction is also different under the comprehensive influence of the above factors.The most serious phenomenon of agglomeration and contraction occurred in the cities of southern sichuan province due to the superposition of most of the above-mentioned factors;(6)the regional spatial structure under the influence of regional development planning policies has a significant impact on the spatial distribution of urban shrinkage,which is exemplified by the obvious phenomenon of shrinkage in the periphery of core development areas and the edge of urban agglomeration within the region.On the contrary,agglomeration and contraction areas still exist in the urban belt determined by the regional development plan and the urban intensive area cultivated by the regional development plan,which runs counter to the strategic goal of supporting the spatial structure of node cities,indicating that the regional development plan should timely judge and respond to this.