近20 a中国省会及以上城市空间形态演变

以多时相、多波段的Landsat TM/ETM+遥感影像为数据源,利用NDBI-SAVI指数提取1990-2010年中国35个省会及以上城市的建设用地信息,通过计算紧凑度和形状指数,研究城市扩张状况,并借助雷达图来分析城市扩张的方向。结果表明:从城市扩张速度来看,东部城市总体上扩张速度高于中部和西部,其中4个直辖市的扩张速度普遍高于其它城市;扩张速度相对较慢的城市多分布在华北和西北等重工业或河谷型城市。从空间形态变化上看,两时期35个城市的形状大都集中于正方形与矩形之间,只有少数城市形状为菱形、星形、H形或X形。综合来看,近20 a中35个城市形状指数的平均值增加,而标准差减小,城市形态趋于复杂;同时,城市紧凑度的平均值减小。有15个城市的紧凑度增加,20个城市的紧凑度减小。城区往往趋向于少数几个方向扩张,"摊大饼"式的扩张不多见。

Spatial-temporal Changes of Urban Morphology of Provincial Capital Cities or above in China

The urban spatial morphology has always been the core field research focus of urban geography. Large city morphology evolution is the result of long-term social and economic development. The dramatic changes of China’s urban spatial form have brought many problems in economic, social, urban construction and urban environment. To understand the progress and mechanism of urban spatial morphology changes, building appropriate quantitative assessment model for urban spatial morphology is significant for promoting China’s sustainable urban development. Since the 1990s, there are new economic and social backgrounds in China. Due to the new mechanism and dynamic characteristics of urban morphology evolution, it is very important to get some new conclusion for the amendment of city theories. This paper summarizes the current research gaps on the basis of narrating the research progress about the evolution of urban form at home and abroad. Then, it chooses 35 Chinese provincial capital cities or above, analyzed the spatial-temporal characteristics of cities’spatial morphologic evolution in recent 20 years not only with the help of multi-temporal Landsat TM/ETM+ remote sensing satellite imagery,urban land use planning map, socio-economic statistical data and other relevant information, but also with ArcGIS 9.3 software platform and Erdas 9.2 software and some different research methods, such as statistical analysis, Boyce-Clark shape indices, compactness indices,trend analysis. The results show that, during the period from 1990 to 2010, the expansion speed of the eastern cities is higher than that of the western and central cities. Among them,the expansion rate of the four municipalities is generally higher than other cities. Relatively slow expansion cities are mainly located in heavy industrial or valley-pattern cities of North and Northwest China. The shapes of the 35 cities are mostly in-between the square and the rectangle in the period from 1990 to 2010, only a few cities in the shape of the diamond, star, H-shaped or X-shaped. Out of 35 cities, 15 cities showed a decreased trend in compactness indices and 20 cities showed an increased trend from 1990 to 2010. The range of shape indices for Chinese cities varies from 6.82 to 69.32 in 1990 and from 7.56 to 65.81 in 2010. Generally, the averages of the shape indices in the two years are 24.9 and 32.09 respectively, which indicated urban morphology tends to be more complicated. The major way of urban morphology evolution of provincial capital cities or above in China is the intension-type development instead of extension transit during the period of 1990-2010. The urban morphology evolution is the result of both inner and outer driving forces, indicating the complexity of urban morphology evolution. This research is highly valued for planning administration and planning practicality, especially at such a high speed of urban expansion and well-developed city planning in China.