长江三角洲地区城市空间扩展研究

城市化是建设用地扩展的主要驱动因素,分析建设用地时空演化格局已成为学者研究城市化过程的重要视角。采用空间自相关等方法,测度了1985年以来长江三角洲地区城市空间扩展的集聚特征并分析其演变过程;并结合格网建设用地密度频率的变化特点,将空间划分为不同的景观梯度地带,以此研究城市空间在不同地带中的扩展特点。研究结果表明,长三角城市空间扩展聚集程度先降后升,城市化区域融合趋势明显,并在城市空间扩展中表现出以上海、南京和苏州等为代表的3种模式,反应了长三角内部不同的经济发展特点。此外,在不同景观梯度下,长三角城市空间扩展表现出典型的阶段性特征。2000年以前在各个景观梯度下城市空间扩展差异较小,表现为较强的拓展性扩展;2000年以后,在城市核心区扩展强度加强,表现为填充式扩展加快。同时,城乡过渡区面积增加迅速,表明随着城市空间扩展的加速,长江三角洲地区城市土地不集约利用现象已较为突出。

The Expansion of Urbanization Area in Yangtze River Delta

The Yangtze River Delta is one of the most developed areas in China. Since the Reform and Open up, this area has experienced dramatic changes in urbanization. In the process of urbanization and industrialization, a large number of agricultural land has transferred to built-up areas for industrial and urban development in Yangtze River Delta, especially in the outskirt of the large cities and the county-level cities which experienced rapid economic and population growth. The construction land was interpreted from the Landsat TM satellite images and acquired in 4 periods of 1985, 1995, 2000 and 2007, which was used as a major index to study the spatio-temporal characters of expansion on urbanization area. By the GIS and RS based study, it was found that the urban spatial sprawl agglomeration (Global Moran’s I) decreased at first from the year 1985 to 2000, then it began to rise. This fluctuation had a strong link to the political and economic development in Yangtze River Delta and China. After detecting the global sprawl agglomeration, many local "hot spots" of urban spatial sprawl were also found as the time went by. From the Getis-Ord Gi^* statistic, the main path of that "hot spots" transferred was studied and three models of urban area sprawl in the 16 cities of Yangtze River Delta are found. They are Shanghai model, which represents the multi-central urban area sprawl. Nanjing mode, which represents the strong single-core urban area sprawl, and Suzhou model, which represents the multi-core (in different scale) urban area sprawl. On the other hand, after statistics the density of construction land in every grid and their proportion changes along the urbanization gradient, the threshold was established to divide the core urban area, urban-rural fringe and rural area in Yangtze River Delta, computing the expansion strength of construction land in every gradient. With those methods, some phenomenon is also found that, before the year of 2000 agricultural land was increasingly turned into urban-rural fringe because of the land was not used sufficiently and little difference of expansion strength among construction land in the three areas. After 2000, the difference is significant, construction land sprawl more active as the urbanization gradient increased.