Study On The Delineation Method Of Urban Growth Boundary Under The Coordination Of Expansion Potential And Ecological Constraint

The rapid urbanization process of China attracts worldwide attention,and the spatial expansion of urban construction land has been the dominant characteristic of land use change in China.At the same time,it comes with some problems that restrictthe cities' healthy development,such as the cultivated land security under threat,the disturbed ecological environment,the incompact and inefficient urban spatial structure,etc.According to international experience,the urban growth boundaries play a significant and positive role to ease the contradiction between economic development demand and the natural resource restrictions,as a policy instrument for urban space growth management.While in China,choices of macro policy,like the National New Urbanization Plan(2014-2020),turn to enhance the control of urban scale and the guidance of expansion,and emphasize the importance of delineating urban growth boundaries.In this context,how to coordinate the contradiction between land development and resource protection,and how to delineate the urban growth boundary scientifically and reasonably,has been a great challenge for cities'sustainable and healthy development in the future.At present,the research on the delineation method of urban growth boundary mainly focuses on the forecast of urban expansion and the delineation of ecological security pattern,which has achieved the goals that the urban scale is controlled effectively and the ecological resource is preserved from occupation to a certain degree.Whereas,less attention has been paid to the impact of the spatial distribution of human activities on the shaping of urban space.Therefore,Changsha central city is chosen as the study area,whose urban expansion potential is significant and constraint function and protect need of ecological resource is obvious.In this study,dependingon the multi-source spatio-temporal data which representing the spatial distribution of human activities,based on the integration of geospatial analysis,geographic evaluation techniques,logistic regression model,cellular automata(CA)model,and other methods,the potential evaluation model of urban construction land expansion is built,and a way of computing the importance index of ecological land is put forward.Furthermore,from the perspective of coordinating the relationship between "urban internal expansion potential" and "external ecological constraints",the simulation model of urban spatial evolution process based on the evaluation of regional ecological characteristics,which is called the EI-CA Model,is designed and realized.And then,the simulation of urban construction land expansion,the research on delineation method of urban growth boundary is carried out,and also the science and validity of the delineation method is evaluated and analyzed.The main contents and conclusions of this study are as follows:(1)Potential evaluation of urban construction land expansion.The spatial expansion direction of cities is closely related to their internal driving factors.It can reflect the rule of urban growth through the potential evaluation of urban construction land expansion.However,how to accurately grasp the internal driving factors influencing urban expansion,is the key issue of potential evaluation research.From the aspects of population,economy,geographical location,infrastructure layout,this study builds the potential evaluation index system of urban construction land expansion by using nighttime remote sensing images,weibo POIs,and other multi-source spatio-temporal data.The potential of urban construction land expansion is quantified based on logistic regression model.The results show that the economic change,the distribution of urban residents' activities,the distance from the main road,and the permanent population density are the most significant variables to the urban construction land expansion.Moreover,there is huge spatial differentiation among the potential of urban construction land expansion.(2)Importance evaluation of ecological land.As the potential supply land for urban expansion,the ecological land should be the key research area for urban growth management.In this regard,this study designs the calculation method of ecological land importance based on the integration of USLE model,InVEST model,HSI model from the aspects of "ecosystem services" and "ecological requirements".The results show that the areas with the highest ecological importance index(EI)in the study area include forest parks,wetland parks,non-commercial forests which provide important ecosystem services(biodiversity conservation function,soil conservation function,carbon sequestration function),along with the scattered ecological patches,such as r forest land and water,which meet the high ecological requirements.While,the areas with relatively low El are mainly farmland and grassland which are distributed in the suburbs.(3)Delineation of urban growth boundary.Aiming to the conflict coordination between urban development and ecological protection,this study proposes the design idea of coordinating the relationship between "urban internal expansion potential" and"external ecological constraints".Based on the evaluation results of urban construction land expansion potential and ecological land importance,the EI-CA Model is built,the evaluation of areas which are not suitable for construction and the simulation of urban construction land in suitable region are realized.And then,the urban growth boundary is delineated.The analysis of delineation result shows that the urban development boundary matches the spatial pattern of urban development,which means that the forecast of construction land expansion in the future makes sense.Moreover,the delineated boundary avoids occupying important ecological resource and guides the city to expand in suitable area.Generally,the goal to balance the urban development and ecological protection is achieved.