土地利用变化的地形梯度特征与空间扩展——以北京市海淀区和延庆县为例

选择北京市海淀区、延庆县作为研究区,利用1992年、2002年遥感影像数据,借用地形位梯度指数,研究了土地利用变化的地形梯度特征及其空间扩展形势。研究表明:(1)海淀区建设用地受到经济和社会发展驱动明显,表现出既向低地形梯度位也向高地形梯度位扩展;但农业用地、果园因建设用地扩展受到挤压,表现为向更高地形位扩展态势;林地在高地形位得到了明显恢复,也有向更低的地形位扩张的趋势,但灌草地和未利用地在中高地形位受到林地挤压,低地形位受到农业用地、果园挤压,优势地形位明显萎缩;(2)延庆县建设用地扩展受地形位驱动作用明显,主要集中在低地形位区域;农业用地主要分布在较低地形位上,变化不大;果园在经济发展需求驱动下,向更高地形位扩展;林地在较高地形位得到较好恢复,对灌草地、未利用地产生了挤压作用,使得灌草地、未利用地在中高地形位的优势度降低,优势分布区间趋于萎缩。

Land use change characteristics along the terrain gradient and the spatial expanding analysis: A case study of Haidian District and Yanqing County, Beijing

Studying land use change and its spatial expansion along the terrain gradient is of great significance for identifying the direction of land use change and its sustainable use.In this paper,a case study was conducted in Haidian District and Yanqing County of Beijing by comparing land use pattern in 1992,and 2002 with regard to terrain niche index using remote sensing image interpretation.It was found that:(1) A clear difference exists in land use change between Haidian District and Yanqing County.In Haidian District,the built-up area expands to both higher and lower terrain niche areas with economic development and population growth.Farmland and orchard are extruded to the higher terrain niche area due to urban expansion.Woodland in high terrain niche area is well restored,and further expands to the lower terrain niche area.The unused land,grassland and shrubberies are remarkably constricted in the middle and high terrain niche areas with the intrusion of woodland,and reduced in the low terrain niche sections due to farmland increase.In Yanqing County,the built-up area is obviously confined by the terrain niche and is mainly located in the low terrain niche area as well as the farmland.Orchard,however,is shifted to the higher terrain niche area with the economic development.Woodland is well restored in the higher terrain niche area,and the predominant distribution of the unused land,grassland and shrubberies is reduced.(2) A common point was found in both Haidian District and Yanqing County.Ecological conservation was well carried out in the both areas in recent decade,and consequently natural vegetation was restored appropriately.A difference in land use change is that land use in Haidian District is more affected by the economic development than that in Yanqing County.The built-up area spreads out faster in Haidian District,and farmland was extruded to higher terrain niche area under the pressure of urban expansion in Haidian District,while they are both constricted in the low terrain niche area in Yanqing County.