Abstract: Grassland ecosystem shows an obvious degradation trends in Qinghai-Tibetan Plateau due to global warming and intensity human activities. Many methods have been developed to monitor the grassland degradation. As a representative method, remote sensing technology provides a wide, quick, and accurate approach to reveal the process of grassland degradation. One of the important characteristics of grassland degradation is the decline of vegetation coverage. MODIS data are used to describe the grassland coverage status. Results show that the grassland vegetation coverage remains an upward trend from 2000 to 2011. The upward trend is divided into five grades, which are severe deterioration, slight deterioration, unchanged, slight melioration, obvious melioration. In the source of Yellow River, the trend is more obvious and mainly obvious melioration grade. The restoration process of grassland in the Three-River source region is a fluctuant procedure, while it is steadier in the source of Yellow River. The vegetation coverage is widely recovered in the most area of the Three-River sources region after ecosystem engineering. The decline of vegetation coverage is mainly occurred in the central of Yushu, part of Zaduo and in the eastern of the Three-River sources region.

Key words: The Three-River sources region, Vegetation coverage, Trend analysis, Ecological effects

摘要： 近年来，受全球气候变暖及日趋频繁的人类经济活动的共同影响，三江源地区草地生态系统持续退化，已引起各方面的高度关注，并成为草地生态学界的研究热点。本文利用MODIS长时间序列的遥感观测资料，对三江源地区草地覆盖度的变化状况进行了监测。结果表明：从2000—2011年，三江源地区的草地覆盖度总体趋势保持上升趋势；黄河源地区草地覆盖度恢复特征明显，以明显变好为主；三大流域的草地恢复处于震荡恢复过程，黄河源区相对较为平缓；生态系统工程实施后，三江源地区绝大多数地区的植被覆盖度均出现了不同程度的回升，覆盖度下降的地区主要出现在三江源的东部、中部玉树州以及杂多县的部分地区。

关键词: 三江源, 植被覆盖度, 趋势分析, 生态效应