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北京地区不同地形条件下的土地覆盖动态

LAND COVER DYNAMICS OF DIFFERENT TOPOGRAPHIC CONDITIONS IN BEIJING

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【作者】 吴晓莆唐志尧崔海亭方精云

【Author】 WU Xiao-Pu TANG Zhi-Yao CUI Hai-Ting and FANG Jing-Yun (Department of Ecology & Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, Beijing 100871, China)

【机构】 北京大学环境学院生态学系、北京大学地表过程分析与模拟教育部重点实验室北京大学环境学院生态学系、北京大学地表过程分析与模拟教育部重点实验室 北京100871北京100871

【摘要】 利用MSS/TM影像和1∶250000高程数据分析了1978~2001年北京地区土地覆盖的变化。为研究人类活动对土地覆盖类型及植被变化的影响,根据植被的分布规律和人类活动影响,利用数字高程模型(DEM)将研究区遥感影像分为不同海拔段,分别建立标志进行解译。通过转移概率矩阵计算、不同地形因子影响下的土地覆盖类型分布的GIS分析,得到如下结果:1)1978~2001年间北京市土地覆盖变化主要发生在平原和低海拔、小坡度的平缓地区,表现为农业用地向城镇用地的转变;高海拔地区主要为天然植被所覆盖,土地覆盖变化相对较小,主要是灌丛向林地的转变。2)地形因子显著影响土地覆盖类型的分布及变化。随着海拔的升高和坡度的增大,农业用地和城镇用地减少,林地和灌丛逐渐增加。坡向对植被的分布也有较大影响。

【Abstract】 Topographic conditions play an important role in controlling land cover dynamic processes. In this study, remotely sensed data and geographic information system were applied to analyze the changes in land cover along topographic gradients from 1978 to 2001 in Beijing, a rapidly urbanized mega city in China. The study was based on five periods of land cover maps derived from remotely sensed data, Landsat MSS for 1978, Landsat TM for 1984, 1992, 1996 and 2001, and digital elevation model (DEM) derived from a 1: 250 000 topographic map. The entire area was divided into 10 land cover types: conifer forest, broadleaf forest, mixed forest, shrub, brushwood, meadow, farmland, built_up, water body and bare land. The results are summarized below. 1) Shrub, forest, farmland and built_up consist of the main land cover types of the Beijing area. The most significant land cover change from 1978 to 2001 was a decrease in farmland and an expansion of built_up areas. Farmland decreased from 6 354 to 3 813 km~2 over the 23 years, while built_up areas increased from 421 to 2 642 km~2. Forest cover increased from 17.2% to 24.7% of the total area. The conversion matrix analysis indicated that transformation of farmland to built_up area was the most significant process and afforestation was the primary cause of replacement of shrub to forest. 2) Topographic conditions are of great importance to the distribution of land cover types and the process of land cover changes. Elevation has a strong impact on the distribution of land cover types. The area below 100 m mostly consisted of farmland and built_up areas, and the area above 100 m is mainly covered by shrub and forest. Shrub has a maximum frequency in elevations between 100 and 1 000 m, while forests were dominant in areas above 800 m. According to the analysis of land cover changes in different elevation ranges, the greatest change was below 100 m due to urbanization. The main land cover change process that occurred above 100 m was transformation from shrub to forest. This result was constant with the vertical change of natural vegetation distribution in Beijing. 3) Slope has a large influence on the distribution of land cover types. Farmland and built_up areas are distributed primarily in flat areas, while shrub and forest occupy steeper lands as compared with other land cover types. Forest frequency increased with increasing slope. Land cover change processes differed with slope gradients. In the plain area, land cover change occurred as the result of urbanization. With increasing slope gradients, afforestation, which converted shrub to forest, was the primary land cover change process.

【基金】 国家自然科学基金项目(90211016、40021101)
  • 【文献出处】 植物生态学报 ,Journal of Plant Ecology , 编辑部邮箱 ,2006年02期
  • 【分类号】P272
  • 【下载频次】635
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