Spatial Identification And Evolution Of Urban Fringe

Urban fringe in China is viewed as the region space where various impacts of the city area converge,a place full of conflicts of interest.With the abrupt and dramatic transformation of the urban socio-spatial structure,the frequent adjustments and shifts in the structure and function of urban fringe has gradually given rise to conflicts between human and land as well as in land utilization.Therefore,research on urban fringe spatial recognition and characteristics and influencing factors of spatial pattern evolution is of crucial significance to practices such as the demographic management,resource allocation and policy-making of urban fringe.This study conducted an empirical study on the urban fringe of Xi’an City based on theories and methods such as urban geography,landscape ecology and urban allometry growth and mainly using the techniques of remote sensing and spatial analysis of geographic information system to process data collected through remote sensing imaging and social statistics of Xi’an City in 2000 and 2010.It constructs an evaluation framework and the index system of urban fringe area from the perspectives of physics,landscape and population,using the impervious surface coverage and the degree of landscape disturbance as primary indicators,and the population density data as auxiliary indexes.Then,the spatial range of the urban fringe of Xi’an city in 2010 was further quantified in this study by performing the computation of information entropy and mutation detection methods.And we analyzed the characteristics of the spatial evolution in urban fringe with respect to expansion features,landscape features and expansion rationality,and examines the influencing factors of the spatial evolution in urban fringe holistically in aspects such as nature,population,economy,transportation and policy.The final results obtained are as follows:(1)Variability in urban social activities,physical space and landscape pattern are reflected,respectively,by population density,impervious surface coverage and degree of landscape disturbance.And values of all the indices demonstrate unique spatial information in accordance with the urban-rural gradient.Therefore,the urban-rural spatial heterogeneity of the indices can enable the identification of the whole spatial range of urban fringe in a more scientific manner and with better accuracy.The spatial pattern of urban fringe was used to perform quantitative identification of the spatial range of the fringe of Xi’an City in 2000 and2010 through combining landscape,physical and population measurements.The results indicated that the fringe of Xi’an City had expanded from 220.73 to 378.36 square kilometers over the past decade,with a growth rate of 71%.In addition,there was an evidently concentric-circle structure in the administrative area of Xi’an City,consisting of,from inside out,urban core,urban fringe and rural hinterland.(2)The urban fringe spatial evolution of Xi’an City was basically in a concentric-circle expansion pattern.During the research,the expansion rate of the fringe of Xi’an City was evidently higher than that of the core area,showing a significant anisotropy in the expansion directions,with the expansion in the southern and southwestern directions being of high momentum.The expansion in urban fringe was predominantly outbound,with the indigenous demand accounting for only one third of the trend,while that of the core area of Xi’an City was slower,resulting in an drastic difference in expansion degree between the inner and outer boundaries of the urban fringe.(3)The urban fringe in Xi’an and the peak of landscape fragmentation were almost consistent spatially,providing evidence for the features of urban fringe such as high patch density,small patch size and high landscape fragmentation.The most prominent shift in the landscape pattern over the past decade occurred in the urban fringe,where there is a transition in landscape pattern from being rural-specific to urban-specific.The human-land relationship in the downtown area of Xi’an City corresponded with the allometric growth.Specifically,land area per capita had increased with the expansion of the city but the land resources were not utilized intensively,which,to a certain extent,indicated that Xi’an City had witnessed a high-speed economic growth over the past decade.(4)The emergence and evolution of urban fringe has been influenced by various factors in different time and spatial measurements,such as nature,population,economy and transportation.The expansion of the fringe of Xi’an City had two thrusts: the southwest and northeast,mainly shaped by the local geological conditions and driven by the integrated construction in the Xixian New Area.Substantial population increases were mainly found in the fringe of Xi’an City,which in turn fueled the drastic expansion of the area.During the process,the urban transport network developed based on the axis and concentric circles in the radiating pattern helped guide the expansion of the fringe area,and urban planning and construction of the New Area effectively promoted the development of the area,ensuring that the evolution was on the right track.