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Landsat TM/ETM+ sensor data has proven to be a highly effective data source for vegetation and land use classification at both global and regional scales. In this study, based on land cover classification, we conducted computer-aided analysis of degradation sequence of the meadow grassland in Xilin River Basin, Inner Mongolia, using 4 sets of Landsat TM/ETM+ images (WRS 124-39 and 124-30) acquired on Jul.31, 1987, Aug.11, 1991, Sep. 27, 1997 and May 23, 2000, respectively. Primarily, 17 sub-class land cover types were recognized, including 9 grassland types at community level: F. sibiricum steppe, S. baicalensis steppe, A. chinensis + forbs steppe, A. chinensis + bunchgrass steppe, A. chinensis + Ar. frigida steppe, S. grandis + A. chinensis steppe, S. grandis + bunchgrass steppe, S. krylavii steppe, Ar. frigida steppe and 8 non-grassland types: active cropland, harvested cropland, urban area, wetland, desertilized land, saline and alkaline land, cloud, water body + cloud shadow. Then we created thematic maps of the areal change and spatial variation of the meadow grassland in Xilin River Basin, Inner Mongolia. We used Geographical Information System (GIS) tools to create thematic maps of the meadow grassland and then analyzed its degradation sequence (or the evolution route). Driven by overgrazing, the meadow grassland ecosystem in Xilin River Basin, Inner Mongolia had undergone and was undergoing degradation evolution; the evolution route was from meadow grassland (F. sibiricum steppe, S. baicalensis steppe), via temperate grassland (A. lymus + bunchgrass steppe, A. lymus + forbs Steppe, A. lymus + S. grandis steppe, S. grandis + bunchgrass steppe, S. grandis + forbs steppe and A. lymus + Ar. frigida steppe) to desert grassland (S. krylavii steppe and Ar. frigida steppe). Results of this study show that increasing human population and accelerated social-economic development has caused dramatic degradation and fragmentation to the grassland ecosystems in Xilin River Basin.
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