A Space-time Evolution Research On Urban Spatial Expansion And Ecological Carrying Capacity Of Chongqing Section In The Three Gorges Reservior Area

In the report of the 19th National Congress of the Communist Party of China,president Xi pointed out that we will accelerate reform of the system of ecological civilization and build a beautiful China.In the background,the importance of the concept of Eco-city is becoming more and more prominent and the contradiction between urban expansion and ecological environment protection has become a pressing issue of Chinese sustainable development.Aiming at grasping the essence of urban spatial development,reflecting the degree of ecosystem stability objectively and providing theoretical support for the construction of Eco-city,this paper studied the evolution characteristics and laws of urban spatial form and ecological carrying capacity.It provided the decision-making reference for the sustainable development of the reservoir area as well.Based on summing up the theories and research methods regarding urban spatial expansion and ecological carrying capacity of domestic and foreign scholars and depending on remote sensing data,land use data,meteorological data and social and economic statistics,etc,in the first place,this paper quantitatively calculated the index covering the urban expansion intensity index,velocity index,compactness index,fractal dimension,shape index and spatial anisotropy and discussed the past 20 years`evolution characteristics of urban spatial form in the three Gorges Reservoir,Chongqing area;next,by taking into account many factors including“nature,society,economy and ecology”,it constructed the comprehensive evaluation index system of ecological carrying capacity as well as quantitatively analyzed the spatial and temporal characteristics of ecological carrying capacity from three angles of ecological elasticity,bearing pressure and bearing capacity through applying the comprehensive evaluation method;and in the end,this paper discussed the coupling mechanism between urban spatial expansion and ecological carrying capacity,put forward the coupling model and calculated the coupling degree and coupling coordination degree quantitatively.Meanwhile,it also studied the level of coupling action and spatial distribution from two dimensions of time and space.The result indicates that:(1)City built-up area scale of study area is increasing year by year from 232,491km~2 in 1995 to 136.4063 km~2,nearly 6 times.In particular,after 10 years,since Chongqing became municipality,both the intensity and shape of city expansion changed a lot affected by local policy.City built-up area presents the space pattern of“Large Centralization and Distribution”which looked like plum blossom spot taking the Yangtze river as the main axis.(2)In the study area,there are obvious differences in the regionalization of urban expansion.It is obvious of the interaction and interplay between the urban expansion of each district and county.Urban construction in Metropolitan area gradually breaks the morphological pattern limitation of“two rivers and four mountains”.Cities of the middle and northern regions are approaching the western part in a zonal pattern along Yangtze River,forming a spatial layout pattern of“one center,multiple group”,which continuously forms urban agglomeration and urban belt of three Gorges Reservoir area,showing the unique urban style of Mountain City of“mountains are cities and cities are mountains”and“Along the river,there are cities and they embrace the river”.(3)The average ecological carrying capacity of the study area is around 0.5,at a medium stable level;its index is rising steadily,and the spatial distribution is characterized by"low in the west and high in the east"and also gradually decreases from the northeast China with strong bearing capacity to the west with weak bearing capacity.In the process of Eco-city construction,corresponding strategies or suggestions should be put forward for different natural endowment and social and economic development level of different districts and counties..(4)Coupling degree indicates the strength of interaction degree between urban spatial expansion and ecological carrying capacity,while the degree of coupling coordination indicates the level of coordinated development of the coupling degree in the interaction between urban expansion and ecological carrying capacity.Through the spatial combination of them,we found that there are five types of spatial combinations in the study area like the coupling of low intensity and coordination,the coupling of medium intensity and low coordination,the coupling of medium strength and low coordination,and the coupling of medium strength and high intensity coordination.(5)The coupled effect of urban spatial expansion and ecological carrying capacity is relatively low in the study area,most of them in the stage of low intensity and low coordination coupling with obvious spatial differences.Apart from Shapingba District,Yubei District,Jiangbei District and Nanan District,the coupled effect of other all districts and counties is low.In the future,we should protect the ecological environment during expanding the scale of cities and towns and go for green development,harmonious development as well as joint development.