北京市1990年～2000年土地利用变化机制分析

根据1990年、1995年和2000年3期影像资料，运用遥感平台获取了北京地区90年代的土地利用变化时空数据，结合历史气象数据、水文数据及其它空间、属性数据，运用GIS空间分析方法及数理统计方法，全面分析了北京市1990年～2000年间土地利用变化的空间特征及其驱动力。揭示该区各类土地利用数量变化的幅度、速度和区域差异。针对变化幅度最大的城镇用地运用空间重心转移模型、分形模型分析90年代北京城镇用地扩张的空间变化特征和区域方向。研究结果表明：北京地区1990年～2000年间土地利用变化的主要方向为城乡居住建设用地不断扩张，林地与耕地变化类型占土地利用图斑总数的5.5%以上。全区耕地面积减少93 749hm²，林地、园地面积增加了12 106hm²，居民点等建设用地面积大幅度增加77 674hm²；北京地区10年来土地利用年变化速度达到0.95%。耕地以平均每年1.60%的速度减少；城镇建设用地和水域面积年变化率分别达到5.28%和2.86%；1990年～1995年间城镇用地重心转移方向为西北，1995年～2000年城镇用地重心转移为东南方向，城镇用地空间形态不规则程度逐渐降低；通过对影响城市用地扩展的城市人口、GDP因子的偏相关分析发现，经济的发展是城市用地扩展的根本驱动力，第三产业的发展是土地利用多样化转变的外在驱动力，交通条件、环境条件及前期土地利用方式是这一转变的主要内在影响因素。

Analyzing the Mechanism of Land Use Change in Beijing City from 1990 to 2000

The objective of this study is to ascertain the temporal and spatial differences of land use conversion in Beijing.Land use status and land use change information in the year of 1990,1995 and 2000 were extracted by integrating TM images with Remote sense software.We use historical meteorological data,hydrological data and other spatial data to make an in-depth analysis of the changing characteristic based on statistic method in conjunction with GIS,and driving force of land use in Beijing city.This paper illustrates the spatial expansion process and mechanism of urban land utilization through the principal conversion type analysis in 1990s with spatial center of gravity transfer model and fractal model.The more detailed results include: firstly,the main characteristics of the city's land use change are the obvious reduction of the existing farm and the expansion of urban land use along several major roads.The spatial analysis of land use of Beijing shown that the even change rate of land use reached 0.95%. The urban land use grew to(220 131) hm~2 from(147 000 hm~2,) an annual average increase rate of 5.28%.The farm land use decreased from(585 270 hm~2) to(491 521 hm~2,) an annual average decrease rate of 1.60%.Secondly,the direction of gravity transfer of Beijing urban land use is northwest from 1990 to 1995,and southeast from 1995 to 2000.Third,the fractal dimension in different periods is calculated based on the features of different county.The results of analysis suggest that spatial structure of urban land feature in Beijing is obviously fractured.If D>1.5,the shape of the urban system is more complex and is in expansion stage.If D<1.5,the shape is becoming more simple.According to the results of the calculation,the fractal dimension of spatial structure is 1.74378 in 1990,which implies that urban system is in extension stage.With the evolution of urban system,from 1990 to 1995 to 2000,the increased urban area is evenly filled the city,and the D value is decreased from 1.74378 to 1.58778 to 1.27981.Lastly,the development of economy can better explain the expansion of urban land use than urban population with the partial correlation analysis.The external driving forces of expansion of urban land use in Beijing are the rapid growth of urban population and foreign investment.The basic forces of expansion are the transportation issue,topography,land patterns and the policy of government.