Spatial-temporal Features And Evaluation Of Urban Expansion In China’s Major Cities From 1995 To 2015

With the increasing demand for land for urban development,the expansion of urban construction land presents a disorder and irrationality,which not only intensifies the contradiction between the supply and demand of ecological land and cultivated land,but also causes a series of social and ecological problems.At the same time,in the context of rapid urbanization,governments at all levels hope to actively promote the development of urbanization.Therefore,judging the size of the city needs to be analyzed in specific regions and periods,and the policy formulation and implementation of urban construction needs to vary from place to place.This paper takes Landsat TM images from the period of 1995-2015 as the data source,and takes 31 provincial capital cities as the research object.Based on GIS spatial analysis technology,this paper explores the spatial pattern and evolution of construction land expansion in provincial capitals from the perspective of time series and space development.From the three aspects of expansion quantity,expansion direction,and expansion model,this paper analyzes the spatial and temporal characteristics of the expansion of construction sites in provincial capitals,and comprehensively evaluates the types of urban construction land expansion from the aspects of urban form and efficiency.The results of the study indicate that:(1)From the perspective of the number of expansions,there are obvious regional differences in speed and intensity for the scale of 31 provincial capital cities.Beijing has the largest expansion during 1995-2015,Zhengzhou and Chongqing have the fastest expansion rates,and Nanjing has the largest expansion strength.The urban expansion quantities in most provincial capital cities have increased,and four cities in Guangzhou,Hangzhou,Fuzhou,and Xining have shown some achievements in government-controlled urban expansion.(2)From the perspective of expansion,there are four types of expansion directions,including maintaining the development of multi-polarization,maintaining a single(or two)direction-oriented development,changing from directed expansion to multi-polarization,and multipolarization.Turn to directional development.Topographic conditions,socio-economic drivers,and government-led have become important factors affecting the pattern of urban expansion.(3)For the expansion model,cities that maintain and turn to fill-in expansion model,urban development tends to "smart growth",and cities that maintain and shift to borderline and enclave expansion models need to strengthen the management and effective development of urban land in order to ensure a reasonable urban expansion.(4)From the results of urban expansion evaluation model,in the aspect of urban expansion,the expansion pattern of provincial capitals in the period of 1995-2015 was in the fluctuation of agglomeration and diffusion,and the expansion period of different cities was also in a different time period;in urban expansion In terms of efficiency,the efficiency of the expansion of 31 provincial capital cities is in a stage of improvement and the efficiency of nearly half of the provincial capital cities has increased significantly,indicating that the quality of urbanization has been actively promoted.The efficiency of urban expansion in different regions is related to the way of urban development and the policy environment in which it is located.The research results provide a scientific basis for the overall understanding of the urbanization process in the country and the control and control of urban construction land expansion in various regions.It not only provides a certain reference and reference for the city’s "smart growth" and the formulation of relevant policies,but also provides guiding significance for enhancing the competitiveness of the city and the region’s sustainable development.