近15年来长江黄河源区的土地覆被变化

基于长江黄河源区土地生态分类，利用1986年与2000年两期TM遥感数据的对比和野外实地调查，采用景观生态空间分布格局分析方法，从分布面积变化和类型转移趋向与幅度两方面，分析了江河源区近15年来土地生态系统的空间分布变化与演变格局，结果表明：高寒草地退化显著，较高覆盖度高寒草原与高寒草甸面积减少了15.82% 和5.15%，高寒沼泽草甸分布面积锐减了24.36%；湖泊水域萎缩了7.5%，以长江源区内流湖泊为主；土地荒漠化发展十分强烈，沙漠化土地面积扩展了17.11%，其中黄河源区沙漠化土地年平均扩展率达到1.83%。高寒草原草地的覆盖度下降与荒漠化、高寒草甸草地的覆盖度下降与草原化以及沼泽草甸草地的疏干旱化是区域土地生态系统空间演变的主要趋向，并由此改变了土地覆被的空间分布格局并使该区域生态环境持续恶化。

Land Ecological Changes and Evolutional Patterns in the Source Regions of the Yangtze and Yellow Rivers in Recent 15 Years

Based on land ecological classification in the source regions of the Yangtze and Yellow rivers and field investigation, the two phases of TM remote sensing data obtained in 1986 and 2000 were compared. From spatial distribution pattern variations and type transformation trend, the spatial changes and evolutional patterns of land ecosystem in the source regions of the two rivers were analyzed in this paper using the analytical method of landscape ecological spatial patterns. Results show that high-frigid grasslands degraded obviously by 15.82% and 5.15% for cold steppe and cold meadow areas respectively, and high-frigid swamp meadow area decreased by 24.36%. Lake water area was reduced by 7.5%, especially the lakes in the source region of the Yangtze River. Land desertification is developing rapidly and desertified land area has increased by 17.11% on an average.Desertified land in the source region of the Yellow River is expanding at an annual rate of 1.83%. Analysis of the evolutional pattern of land ecotypes shows that the general tendencies of spatial evolution in the regions are coverage reduction and desertification of high-frigid steppe, cover reduction and steppification of high-frigid meadows, and desiccation of swamp meadow. As a result, land ecological spatial distribution pattern in the region has changed and eco-environment is continually worsening.