| Nowdays,the rapid development of urbanization makes the spatial expansion of Valleytype cities in China,and the urban spatial structure is constantly restructuring and optimizing.However,complex geographical conditions and sensitive ecological environment also have great constraints on the formation and development of cities,and the ecological environment problems are more serious.Therefore,River Valley cities urgently need a theory and method of mutual adaptation and integration with the natural ecological environment to guide the healthy and orderly development of their urban spatial structure.Based on the value concept of ecological civilization in China and the relevant theoretical research on ‘Sustainable Development’,‘Complex Adaptive System’ and ‘Ecological Adaptability’,this paper explores the factors,practical problems and mechanism behind the evolution of the spatial structure of Valley-type cities by analyzing the influencing mechanism of the evolution,so as to construct the ecological suitability evaluation system of the spatial structure.The spatial structure and the adaptability of natural ecology are analyzed quantitatively and qualitatively,and the typical Valley-type cities,Xichang City of Sichuan Province,are taken as empirical objects,in order to fully integrate theory with practice and ensure the value and significance of the research.There are 6 chapters in this paper,which are mainly divided into 4 parts: research origin,theoretical research,empirical research and conclusion.The first chapter is about the origin of the research.It elaborates the research background,purpose and significance,clarifies the research object and content,clarifies the research innovation and key issues,and introduces the methods and framework.The second,third and fourth chapters are the theoretical part.Firstly,based on the definition of related concepts,the research progress and basic theory at home and abroad,the spatial structure and its adaptive connotation from the perspective of natural ecology are further clarified.Secondly,it analyzes the urban spatial structure characteristics and dominant influencing factors of river valley cities at different stages from time and space dimensions,summarizes the real problems in the evolution of urban spatial structure,and explains the internal mechanism of the evolution of river valley urban spatial structure,namely It is composed of the combination of natural ecological constraints,policy and institutional guidance,socio-economic driving force,historical and cultural shaping force and traffic technology orientation force.Finally,combined with the research ideas of ecological suitability analysis and ecological carrying capacity analysis,using Delphi Method(Expert Investigation Method),Expert Scoring Method,Analytic Hierarchy Process(AHP),Ecological Footprint Method,relying on the GIS technology platform,the evaluation system of the adaptability of the spatial structure of Valley-type cities from the perspective of natural ecology is constructed.In the 5th chapter,the core of empirical research is the ecological suitability evaluation of urban spatial structure in Xichang City.Through field research,the basic situation and ecological problems are analyzed,and the characteristics of the evolution process of urban spatial structure are sorted out.Then the comprehensive evaluation results of the ecological suitability of urban spatial structure in Xichang City are analyzed.It is found that the underlying causes lie in the fragile natural ecological base,serious environmental pollution,disordered urban spatial layout,unbalanced economic and industrial structure,disordered road traffic network,lagging infrastructure construction,loss of urban historical features and poor quality of greening landscape.Finally,combined with the current problems and development direction,the optimization suggestions of urban spatial structure are put forward from five aspects: ecological security,industrial structure,urban green space,historical context and infrastructure.Chapter 6 is the conclusion,which combs the main research conclusions and puts forward the research prospects. |
