干旱区生态环境知识资源中心

Using four Landsat TM & ETM+ images which obtained in 1989, 1994, 2000 and 2005, the normalized difference vegetation index (NDVI) was calculated on the basis of the geometry correction, radiometric calibration and atmosphere correction, and the assimilation of the NDVI images was made by establishing the least squares equation of linear regression, and extracted the vegetation coverage from the NDVI and converted it into the desertification index (DI) based on the binary model, the classifiable research was made on the desertification of grassland about 103 km(2) near the Litang county. The result demonstrates that: (1) Desertification in Litang County has been deteriorating in the past 16 years (1989-2005). The 1(st) stage (1989-1994) saw decreased desertification area, the 2(nd) stage (1994-2000) observed radical deterioration, and the 3(rd) stage (2000-2005) witnessed slack in this regard. (2) Tendency of desertification has nothing to do with precipitation and wind speed. (3) Human activities e.g. overload over grassland and disorder explorations etc are considered the main causes in exacerbating desertification. (4) Expansion desertification area slowed down during the 3(rd) stage (2000-2005), which ecological restoration projects in China have brought about marked effects.