南京市区建设用地扩张模式、功能演化与机理

Patterns, functions and underlying mechanisms of urban land expansion in Nanjing

以南京市区不同时段遥感影像为基础,在综合凸壳方法与公共边方法基础上,通过矩阵分析对1985-2007年南京市区建设用地扩张模式进行划分,探讨不同扩张模式的空间结构特征。结果表明:1 1985年以来,南京市区建设用地扩张迅速。其中,填充扩张由主城区逐渐向外推移,飞地扩张分散在远离主城区的开发区、工业园及大学城内,蔓延扩张则介于二者之间,多表现为前期扩张的继续发展。2功能上,填充扩张由居住主导向居住与工业混合转变;蔓延扩张由居住与工业混合向工业主导转变;飞地扩张一直以工业主导,并伴随科教的区域性集中。3驱动机理,填充与蔓延扩张属于收益驱动型,飞地扩张更多地受成本制约。随着城市空间向外拓展,建设用地扩张的成本约束作用均逐渐加强;而城市建设用地中工业用地比重的增加,又使三种扩张模式的收益驱动作用加强。

As the largest developing country in the world, China has faced the most serious challenge to urban land expansion, which is rare in the world. Drawing upon the Landsat TM satellite images of Nanjing in 1985, 1995, 2000 and 2007, this paper integrates convex- hull analysis, shared boundary analysis and matrix analysis to distinguish different types of urban land expansion. We also investigate the restructuring of urban land in the course of spread expansion. The results showed that Nanjing has experienced rapid expansion of construction land from 1985 to 2007. And the infilling expansion was initially focused on the areas near the city center, and showed a trend of outward expansion recently; the enclave expansion was centered on development zones, industrial parks and university towns, which were disconnected from the original urban area; the spread expansion was not only concentrated around the original built-up areas, but also expanded from the previous enclave areas. With respect to the functional characteristics of newly developed urban land, the infilling expansion was initially dominated by residential land and was recently featured by a mix of residential and industrial land; the land expansion was characterized by a mix of residential and industrial land, while it has shifted towards land for industrial purposes; the enclave expansion was consistently dominated by land for industrial purposes, along with land expansion for science & education purposes. The new types of urban land use was characterized by the strengthening of its original function,which reflected a rapid industrialization process. Results derived from regression analyses of influencing factors further pointed to the following findings: the infilling expansion and the spread expansion were demand-driven; in comparison with the infilling expansion, the spread expansion was more sensitive to demand-related factors; and the enclave expansion was mainly cost-driving. We also found that, with the continued urban expansion, the expansion of built-up area was increasingly constrained by cost-related factors. However, with the increased proportion of industrial land, revenue-related factors have been strengthening their roles. In the future,the local government of Nanjing should play the role of the central city in the Yangtze River Delta and intensify Nanjing metropolitan governance by making up scientific and rational urban plans, adjusting the structure of the construction land, accelerating industrial restructuring and upgrading, and promoting the development of sub-centers as well.