| China is in the critical period of urban transformation,the urbanization process is accelerating,the urban construction land begins to expand blindly.The extensive mode of growth has caused the serious waste of resources and environment,and the cultivated land resources have been occupied,and part of non-agricultural cultivated land has become irreversible.The Academician Lu has pointed out that the disorderly expansion of urban construction land in our country is obvious,and the situation of losing control of space is serious,which will seriously hinder the process of modernization of our country.In 2015 central cities work conference pointed out that the development of Chinese cities should establish "smart growth" and "compact city" concept,to prevent the "pie" type expansion,promote green low carbon production way of life and urban construction.Therefore,it has an urgent and important social and economic background to prevent the "pie" type expansion,to study the process of space-time evolution of urban construction land,and to adjust and control urban construction land.Land provides carrying space for urbanization,but different from general land use,urban construction land is produced and expanded because of the formation and development of cities,and plays an important role in regulating and controlling urbanization.Among the existing research results,the research on urban construction land is mainly focused on the evolution and expansion of urban construction land and so on.Few scholars study the spatial structure and trajectory of urban construction land expansion,and most of the studies focus on the eastern coastal cities,but for the western cities,the typical cities are less studied.Based on above,this paper takes Chongqing,a typical mountainous city,as the research object,using land change survey data and remote sensing image data to analyze the overall expansion intensity of urban construction land,the spatial agglomeration characteristics,the expansion structure and trajectory measurement,and its expansion drive for identification.The main body of the study consists of the following four parts:Firstly,the expansion intensity of urban construction land in Chongqing is analyzed.It is found that the urban construction land in Chongqing has been developing steadily after 1997,and the overall expansion intensity in 2009 is higher than that before 2009.In spatial differentiation,the intensity of urban construction land expansion has a certain degree of agglomeration in space,the urban construction land in the main-city and its surrounding areas has always maintained a moderate and high-speed growth,and the agglomeration scope is closely related to the urban development policies implemented at different stages.In the northeast of Chongqing,the development of Wanzhou district and the surrounding districts and counties form a linkage development,the urban construction land expansion is stronger;the industrial base of Qianjiang district is weak,and the urban construction land expansion is slow.Secondly,the spatial distribution exploration tool is used to further quantify the clustering characteristics shown in the whole.The quantitative results show that the expansion of urban construction land on the whole shows the process of "random distribution-agglomeration-reagglomeration".The increase of urban construction land area in 1997-2000 presents a random distribution of spatial distribution.From 2000 to 2005,the expansion of urban construction land started from random distribution to agglomeration distribution,and the space began to expand the hot area of land expansion.From 2005 to 2010,the expansion of urban construction land was further strengthened in the space,and this stage formed the distribution pattern of cold hot spots in the "one cold and one hot" urban construction land expansion.From 2010 to 2015,the extension of urban construction on the space of situation more obvious compared with the previous stage,and the cold hot spot spatial distribution pattern of "two cold and one hot" urban construction land expansion is formed at this stage.Thirdly,break through the administrative boundary,further from the perspective of more microscopic spatial patches,by building growth polar core and polar belt model of urban construction land,the urban construction land expansion structure and trajectory of Chongqing directly under the jurisdiction of the measurement.It is found that the spatial changes of the growth of urban construction land are as follows: "one core two belts","one core two belts","two cores two belts" and "two cores four belts".In 1997-2000,the spatial growth structure of urban construction land was "one core two belts",among which the "one core" is Jiangbei district,and the "two belts" are the G212 and the G318-Wan-Da-Yi railway combination line.The spatial growth structure of the urban construction land in the 2000-2005 period is "one core and two belts",among which the "one core" is Shapingba district,and the "two belts" is the G318-Wan-Da-Yi combination line and the Inner ring highway.Phase from 2005 to 2010,urban construction land spatial structure growth of "two cores two belts",the "two cores" are Shapingba district,and Jiulongpo district,respectively,the "two belts" are G212 highway,G212-G205 highway combination line.From 2010 to 2015,the spatial growth structure of urban construction land is "two cores and four belts",the "two cores" are Jiulongpo district,Shapingba district,respectively,"four belts" are S212,Yin-Kun high speed,Yu-Xiang railway and Yu-Sui railway-Lan-Yu railway combination line.Finally,it identifies the driving force of urban construction land expansion of Chongqing.Overall,from 1997 to 1999,the surface had a greater influence on the natural conditions of urban construction land expansion,natural condition as a primary driver of this phase,river system in the early once had a significant impact on promoting urban construction land expansion,the late effects gradually weakened.From 2000 to 2008,the urbanization construction in Chongqing urban construction land expansion force is more outstanding,be the first big driver at this stage,prompted the urban construction land expansion began from random distribution to offer distribution,and the hot spot of land expansion is beginning to appear in space.Driving force from 2009 to 2015,the infrastructure construction to speed up the growth,the late with the improvement of the Chongqing highway,rail,road network,such as highway,railway infrastructure construction of urban construction land increase gradually,the influence of urbanization construction and driving force to form two powers go hand in hand.Between 2009 and 2015,the driving force of infrastructure construction accelerated.In the later period,with the improvement of highway,railway network,high-speed,railway and other infrastructure construction in Chongqing,the impact of infrastructure construction on urban construction land growth was gradually significant.The construction of infrastructure and the driving force of urbanization together form two dynamic forces.The difference of the driving force at different stages and the difference in development speed have contributed to the gradual change of the intensity of urban construction land expansion.The driving force of urban construction land expansion in various districts and counties is different,but it is mainly the result of urbanization,infrastructure construction and financial policy.The Main-city and surrounding counties are the types of external forces driven by infrastructure construction and financial policies,and the space intensity of urban construction land is relatively high.In the southeast and northeast of Chongqing,the urban construction land has a low spatial intensity.The urbanization drive type is more balanced in the early stage of spatial distribution,and the latter is gradually distributed in the northeast and southeast of Chongqing.Financial policies such as "increase?decrease and hang" and "land ticket" have played an important driving role in the expansion of urban construction land.The infrastructure driven type is scattered in the early stage and mainly concentrated in the main city and surrounding areas in the latter stage.The difference of driving force development level and speed in different regions,the difference of driving effect of their respective regional central cities,lead to the change of spatial agglomeration degree of urban construction land expansion intensity and the appearance of urban construction land expansion cold and hot point. |
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