中文摘要：

利用遥感数据和野外调查数据分析了沙漠化与地表定量参数之间的关系，提出了Albedo-NDVI特征空间的概念以及基于Albedo-NDVI特征空间的沙漠化遥感监测模型，即沙漠化遥感监测差值指数模型（DDI）。这个模型充分利用了多维遥感信息，指标反映了沙漠化土地地表覆盖、水热组合及其变化，具有明确的生物物理意义。而且指标简单、易于获取，有利于沙漠化的定量分析与监测。

英文摘要：

Normalized Difference Vegetation Index （NDVI） and land surface albedo are very important biophysical parameters of land surface. In this paper we analyzed quantitatively the relationship between the severity of desertification and vegetation index （NDVI） and albedo. Through experiment and theoretical reasoning, we pro- posed a conception of Albedo-NDVI space and discussed its biophysical characteristics. Then, we analyzed the locations of different land cover classes and the trajectory of desertification in the Albedo-NDVI space. This knowledge can be used to improve current strategies for desertification mapping and change monitoring, by defining measurements in this feature space. Therefore, we present a methodology to monitor severity of desertification. Desertification field data, available data in the literature, and ancillary data were linked with land cover characteristics （vegetation index, land surface albedo） derived from Landsat ETM ＋ multispectral image. The desertification synthetic index, desertification difference index （DDI） , was produced, which combined information contained in the Albedo-NDVI space. This synthesis index is easy to use and possess biophysical properties of the land surface. We proposed this synthesis index as powerful one for desertification assessment.