城市边缘区空间扩展研究是探讨城市未来空间结构和形态演变的基础。本文基于北京大兴区1994、2001和2006年3期TM遥感影像资料提取城镇用地信息,通过对城市扩展强度、城市扩展梯度、城市边缘区空间扩展模式等建设用地的总体扩张行为进行研究,分析研究区十多年来城市化进程中城镇建设用地扩展的时间过程和空间格局特征,对明确未来城市边缘区土地利用发展方向,提高土地利用效率和城乡建设效益提供基本依据。结果显示,大兴区城市土地利用扩展强度不断增强;中心城区以及中心区面积的不断扩张,导致建设用地在高指数区间集中的趋势明显,农村地区小城镇建设的高速发展使得低指数区间的建设用地面积大幅度增加;根据城市化扩展梯度,大兴区分为城市化高速扩展带、城市化快速扩展带和城市化低速扩展带;紧邻中心区的城市化高速扩展带,以集中连片式扩展为主,该模式在边缘区空间扩展中居于主导地位。城市化快速发展带土地利用以轴向扩展模式为主,轴向扩展稳定地影响着大兴区城市化进程。独立发展模式随着城市经济的快速发展其影响将明显增强,逐渐成为城市边缘区空间扩展的主要形式。

The analysis on spatial expansion of the urban fringe lays the foundation for the research on urban spatial structure and formation evolution in the future. Based on the data of urban land use in Daxing District, extracted from TM remote sensing images in 1994, 2001 and 2006, this article conducts an analysis on the temporal and spatial characteristics of urban land use in the urbanization.process of the past ten years urbanization, through studying the intensity index, gradient index and spatial expansion pattern and other factors involved in the expansion of the built-up areas, and provides basis for identifying the orientation of urban land use in the urban fringe and improving the efficiency of land use and urban and rural construction. The result shows that urbanization of Daxing primarily concentrated on the later study period, with ever increasing in intensity of expansion of the urban land use; construcion lands are distributed in the gradient of urban expansion in an uneven manner, with two stable growth areas, generally in highly urbanized area and rural area whose gradient indexes are above 0.8 and below 0.2 respectively. The increasing expansion of the central urban district and its area has resulted in an evident trend that the built-up areas are concentrated on high index sect:ons, with large-scale increase in built-up areas in low index sections due to the rapid development of small towns in rural areas. The whole district was separated into three levels by the urbanization gradient, i.e., the high speed-urbanization belt, rapid-urbanization belt and slow-urbanization belt.The high-speed-urbanization belt, close to the central district, is in the dominant position, but is declining owing to the restriction of the land supply. Rapid-urbanization belt expands mainly along an axis which has exerted stable impact on the urbanization of Daxing. With the rapid development of urban economy,the separated pattern is becoming a main pattern of spatial expansion of the urban fringe, with an increasingly dramatic influence on the spatial expansion, leading to rapid increase of the number of constructed areas.