中文摘要：

祁连山以北地区是我国西北地区重要的组成部分之一，近年来，人类活动的不断加剧致使祁连山以北的部分地区的生态环境急剧恶化．特别是额济纳旗地区由原来的生态屏障沦为沙尘暴的重要发源地。本项研究采用定量遥感技术，应用最新的全球植被指数（GIMMS）作为数据源，对祁连山以北地区1982—2002年间的植被指数变化幅度及变化趋势进行了研究。结果表明，黑河中游的酒泉盆地和张掖盆地。石羊河流域的武威盆地和金昌盆地，多年植被指数呈上升趋势；而黑河下游的额济纳旗，多年植被指数呈负相关，绿洲呈现萎缩趋势。并对绿洲退化的原因进行了初步分析。

英文摘要：

The area to the north of Qilian Mountain is one of the most important areas in northwest China. Recently, the ecoenvironment in this area has drastically degradated and Ejina Banner has been turned from an ecological barrier into one of the sources of sandstorm. On the basis of quantitative remote sensing results, this paper studies the variation trend of NDVI from 1982 to 2002 in the area to the north of Qilian Mountain by using GIMMS NDVI data. It is shown that the variation trend of secular NDVI is rising in Jiuquan, Zhangye, Wuwei and Jinchang basins. On the other hand, the variation trend of secular NDVI in Ejina Banner, which is located in the downstream of Heihe River, is declining and the oasis is shrinking. The mechanism of oasis degradation is also analyzed in this paper.