南京城市扩展过程中聚落斑块的行为特征

城市化过程具体表现为聚落斑块在景观上的消涨过程.基于南京地区1988、1998和2003年的Landsat TM影像,将聚落斑块按演变形式分成新生、消亡、延展、收缩、融合、分裂和混合7种变化模式,分析了各类斑块沿城乡梯度带的分布格局.结果表明:1998-2003年研究区聚落斑块的总面积迅速增加,斑块数量、平均斑块面积和最大斑块指数等均保持同步增长趋势,新生型与混合型构成斑块演变的主体,但收缩和消亡斑块的负贡献率也持续上升;各演变类型斑块沿城乡梯度带的空间分布格局在2个时段上不尽相同;1988-1998年,混合型斑块在主城区表现为高密度扩张;1998-2003年则表现为低密度蔓延,主城区外各梯度带则没有明显的阶段性差异,新生斑块的城乡梯度格局在2个时段基本一致,其密度、面积比例在主城区较小,城市边缘区较高,向外则随离主城区距离的增加而递减;延展斑块前一时段在主城区与远郊存在2个高发区,但后一时段远郊的密度与面积比例均显著降低;收缩斑块和消亡斑块的高发区位于主城区及其边缘和远郊;比较各类斑块的城乡梯度格局发现,城市化程度高、速度快的区域,同时也存在相对快速的斑块收缩与消亡过程,主城区与城外各梯度带在扩展模式上存在阶段性差异.

Behavioral characteristics of settlement patches in urbanization of Nanjing

Urbanization is mainly represented as the expansion or shrinkage of settlement patches from the perspective of landscape dynamics. Based on the Landsat TM images of the Nanjing metropolitan region in 1988, 1998 and 2003, seven evolution types of settlement patches, i. e. , newly generated, dissolved, expansion, shrinking, fusion, division, and multiformity were distinguished, and the patch-specific patterns for the major types along the urban-rural gradient zones were studied with buffering analysis. The results demonstrated that the total area, patch number, mean patch size, and maximum patch index of the settlement patches increased dramatically in 1988-2003. Though the newly generated and muhiformity patches took the greatest proportion of all the changed patches, the areas of shrinking and dissolved patches increased simultaneously. The distribution pattern of different evolution type patches varied along the urban-rural gradients. In the main city region, the patch density of muhiformity patches was much higher in 1988-1998 than in 1998-2003, whereas no obvious difference occurred in other gradient zones. The newly generated patches showed similar patterns in the two periods. In the main city region, the patch density and the area proportion were relatively small; while in the urban fringe area, they were higher, but declined with the increasing distance to the urban center. There were two peaks of the expansion patches in the main city region and the exurb area in the first period; while in the second period, the number and area decreased obviously in the exurb area. The shrinking and dissolved patches mainly distributed in the main city region, urban fringe, and exurb area. As a whole, there existed a shrinking and dissolving process together with the fast urbanization, and the main city region and suburbs had different sprawling rhythms.