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Changes of land-use policy and herdsmen settlement in mid-1980s have significantly altered the diversity of vegetations in aid grazing ecosystems. To examine the spatial dynamics of vegetation species and the changes of carbon source/sink, ecological survey, accompanied with 3S technology, had been applied in this study. A total of 1169 vegetation samples were collected along two 5 km transects, along with topographic and demographic variables (slope, aspects, population, distance from the center of new herd farms). Analysis of this dataset revealed that more than 1/3 of the lands were in serious degradation with dominant unpalatable plant community. The increase in the abundance of inedible plant Peganum harmala in sunny slope near the farm and some annual unpalatable species in the lower land indicated serious degradation of grassland. The roads, the heavily used patches, impacted plant cover greatly, a decrease of 24.8% comparing to adjacent patches. This field experiment demonstrated that there were significant relationships between plant cover and two driving factors; slope degree and distances from the new farm center; on the other side, the results of spatial data analysis provided basis for improving the grassland carbon balance condition. In general, plant cover declined with increases in slope and decreases in the distance. (C) 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of Conference ESIAT2011 Organization Committee.