Chin J Plant Ecol ›› 2006, Vol. 30 ›› Issue (2): 239-251.DOI: 10.17521/cjpe.2006.0033

• Original article • Previous Articles     Next Articles

LAND COVER DYNAMICS OF DIFFERENT TOPOGRAPHIC CONDITIONS IN BEIJING

WU Xiao_Pu(), TANG Zhi_Yao, CUI Hai_Ting, FANG Jing_Yun   

  1. Department of Ecology & Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, Beijing 100871, China
  • Accepted:2005-06-17 Published:2006-03-30

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 km2 over the 23 years, while built_up areas increased from 421 to 2 642 km2. 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.

Key words: Land use/Land cover, Topographical factors, Conversion matrix, Remote sensing, DEM, Vegetation