中文摘要：

为了解宁夏盐池县土地沙化变化，基于NDVI和植被覆盖度遥感定量模型，选取1989、1999和2003年8月的TM遥感影像3景，通过在归一化植被指数（NDVI）阈值划分沙化等级，得到沙化土地等级图。通过对3时段不同类型的土地沙化比较分析，结果表明：盐池县土地沙化变化趋势明显，尤其是流动沙地和非沙化土地，2003年较1989年变化分别为-64．64％和303％。同时，这种变化从另一个角度说明了盐池土地沙化在此时段内出现了逆转；这主要归功于荒漠化治理措施（包括退耕还林、禁牧封育等）以及降水增加等多种因素。与此同时，在生态环境建设过程中，原有固定沙地和非沙化土地发生退化，因此，今后的治理工作应该加大对固定沙地和非沙化土地地区的保护工作。

英文摘要：

In order to understand the change of sandified land in Yanchi County ,Ningxia, grade maps of deserlified land were obtained based on NDVI and quantificational remote sensing model on vegetation fraction, 3 Landsat TM images shot in Aug 1989, 1999 and 2003 in Yanchi County, Ningxia and NDVI divi sion of desersified the grade, comparising and analyzing the sandified land of different types in 3 phases. The results showed that the changing tendency of the sandified land was obvious, especially in the shifting sandy landand the unsandified land. From 1989 to 2003 the area of the shifting sandy land and the unsandified land increased sharply by -64. 64% and 303% respectively, indicating the reverse of desertifaction in this region. It mainly attributes to desertification controlling measures （such as converting croplands to forests, closing and fencing） and increasing rainfall. Meanwhile, in the process of ecological environment construction, the fixed sandy land and the unsandified land were degraded, so, more attention should be paid to the protection of fixed sandy and unsandified lands.