Abstract: Chinese grassland ecosystem plays an important role in economic development and ecological services of this country. In recent decades, this ecosystem is facing challenges of degradation due to heavy population pressure and overgrazing. Based on the conventional evaluation on the lost value of rangeland due to degradation, an improved model was used to reevaluate the lost value with the MODIS data of 2003 and 2005, and the spatial distribution pattern of the lost value of Chinese grassland ecosystem was developed. The results showed that from 2003 to 2005, the total lost value of Chinese grassland ecosystem services due to degradation was 66.603×10⁸US$. The area with a lost value of 0-1000 US$·km^-2 was about 1/4 of the total area of measured grasslands, and that with a lost value of 1 000-3 000 US$·km^-2 was about 1/3 of the total. The seven provinces of West China including Inner Mongolia, Xinjiang, Tibet, Qinghai, Gansu, Yunnan and Sichuan had a lost value of 52.219×10⁸US$, accounting for 78.41% of the total, among which, Inner Mongolia had the largest loss, occupying 25.89% of the total.

Key words: Water stress, Photosynthesis rate, Water use efficiency, Diurnal change, Fraxinus mandshurica