Land Development Threshold Calculation And Landuse Structure Optimization Of Nanjing City

In recent years, the scale of land development has been grown rapidly with population growth, the economy development and urbanization. The situation of over-expansion land development caused a series of problems such as the irrational structure of land use, environmental degradation and so on. The rational allocation of land resource and protection face a severe test. In order to satisfy the need of land resource development and management, the paper proposes a new index called land development threshold on the basis of interational research. The land development threshold is a largest land development and the optimal scale which can satisfy the need of social, economic and ecological development. The new index can be influenced by many factors such as economic development and so on.The paper constructes a system model from the natural constraints, environmental protection, food security, land carrying capacity and socio-economic development perspective of the development on the basis of definition of content and analysis of the influenced factors. The system consists of two subsystems:one is the maximum scale of land development system under the constraint of the food securitye and ecological safety, and the other is the optimum scale of land development under the constraint of regional ecological sustainable development and moderate population. The system model takes Nanjing as an example to appraise the regional land development. The results show an overall urban> rural> suburban counties of the distribution of the land development threshold in Nanjing. The scale of land development is more than that of the optimum scale but not exceed the maximum scale.And what's more the land development is currently in the condition of over zone. Under the current technical conditions and state of economic development, the land development can be developed to a larger scale which means there is a bigger capacity of land development. The lower levels of eco-efficiency can not achieve the maximum overall efficiency of land development.In order to realize the the maximum overall efficiency of land development, especially to realize the ecological benefits, this paper trys to make an optimal allocation of land use structure on the premise of evaluation and calculation to land development threshold. And the program is in line with the actural situation of Nanjing.At last, the paper makes several suggestions according to the results.