Research On The Evolution And Optimization Of Urban Agricultural Structure In Xi'an

Urban and peri-urban agriculture(UPA)is indivisible part of metropolis' production-life-ecology system.Adapting to the metropolitan development,based on the practical needs of supply-side structural reform of urban agriculture,this dissertation took the evolution and optimization of urban agricultural structure as the research subject.Following the geography technological route of process-pattern-mechanism-regulation,the dissertation discussed the evolution process,spatial pattern,dynamic mechanism,optimization mode and guarantee policy of urban agricultural structure.Main research contents are as follows:(1)The relevant researches were combed and thought.Centering on the research theme,the paper reviewed the existing researches from four aspects,such as the basic research of UPA,the function and function structure of UPA,the industrial and industrial structure of UPA,the location and spatial structure of UPA.Some controversial and needing further research issues were identified.(2)The connotation of urban agriculture.The paper differentiated five views on the concept of UPA,and held that the cognitive bias of “UPA is the result of natural evolution or an ideal form” and the fuzzy understanding of the essential characteristics of urban agriculture led to the conceptual dispute.It clarified that UPA is the agricultural form with special production characteristics formed during serving urban demand,in and around large cities,“the special industrial structure serving urban demand" is the essential feature of UPA.(3)Discussion on theoretical methods on analyzing urban agricultural structure.(1)Based on the analysis of the general characteristics of modern urban agricultural industrial structure,the dissertation constructed the evaluation index system consisting of eight indicators that correspondingly reflect four aspects of industrial structure of UPA including structural hierarchy,adaptability,coordination,and put up the integrated multidimensional evaluation model,to evaluate structural rationality.(2)Based on the analysis of the functional types,features and relationship between functions,it chosen 12 indicators corresponding five basic functions of UPA,such as supply guarantee,ecological maintenance,leisure service,farmers' income and rural area drive,to construct the index system and method on function evaluation of UPA.(3)Based on the essential characteristics of UPA and the phase of urban demand structure,as well as the homogeneity of urban and rural demand structure changes,the dissertation constructed the "advantage index of agricultural industrial structure"(AIAIS)according to the idea of dividing urban basic and non-basic activities,and proposed the method on defining urban agricultural space.(4)Proposed the basic method to explore the urban agricultural spatial pattern by using landscape analysis method and AIAIS,ARCGIS spatial analysis and visualization methods.(4)Study on the evolution of UPA in Xi'an metropolis.Using theoretical methods on analyzing urban agricultural structure,from macroscopic scale,the dissertation analyzed the evolution process of agricultural structure since the reform in Xi'an metropolis,the results showed that:(1)the agricultural industrial structure presented obvious upward trends,such as the structural level,the proportion of the breeding industry in agricultural internal structure,the proportion of vegetables and fruits grown in the planting structure,the economic efficiency;But the imbalance of industrial structure was still serious,such as food supply space-time structure imbalance,the great gap in efficiency between industrial links.(2)On the functional structures,the multifunctionality fluctuated upward;for the single function,the suppling food function,the leisure service function and the driving rural development function were gradually improved,but the maintaining ecology function and the guaranteing farmers' income function tended to decline.(3)The space of urban agriculture in Xi'an metropolis,along with the urban-rural consumption structural evolution from “survival type” before the 1990 s,“well-off type” in 1990 s,to "enjoyable type" in the 2010 s to "future type" in the future,presented the tendency of continuously extended range boundaries.(5)Explore the urban agricultural space pattern in Xi'an metropolis.On macro,medium and micro three spatial scales,the dissertation analyzed the spatial pattern of urban agriculture in Xi'an metropolis,the results showed that:(1)spatial pattern of urban agriculture has obvious spatial scale effect,medium scale is the ideal research scale for analysis and optimization of urban agricultural spatial structure.(2)On meso-scale,the urban agricultural space pattern in Xi'an metropolis could be abstracted as the structural model of "circles + patches",namely the vegetable industry circle with fine patches in the near suburbs,the large-scale agricultural circle composed of specialized industry blocks in the middle suburbs and the ecological barrier circle dominated by the characteristic ecological agriculture in the outer suburbs.The inner mechanism of realizing multivariate value of farming land,the constraint mechanism of distribution of resource factors and the regulation mechanism of market economy environment and institutional arrangement jointly explained the spatial pattern of UPA.(6)Research on the driving mechanism of urban agricultural structure evolution.Based on the actual situation of Xi'an metropolis,this paper sorted out and analyzed the internal and external factors influencing urban agricultural structure.And then the dissertation discussed the driving forces including the urbanization forces and the non-urbanized forces,and analyzed the driving mechanisms,such as the competition mechanism for agricultural production factor,the pulling mechanism for changing market demand,the induction mechanism of multi-value pursuit,the promoting or blocking mechanism of the policy system,the pushing mechanism of technological progress,and the response mechanism of agricultural business entities.(7)Optimization of urban agricultural structure.Based on the inherent relationship among the urban agricultural structure and the hierarchical nested geographical spatial characteristics,this paper proposed the idea of urban agriculture structure optimization.On macroscopic scale,the goal function and industrial structure of UPA and spatial function division were determined.The functional orientation and industrial structure optimization model of different types of urban agricultural areas were determined in different functional zones on the meso-scale.Five typical urban agricultural production modes were proposed on micro scale.In view of market failure,the paper put forward countermeasures and suggestions to promote the optimization of urban agricultural structure.