中文摘要：

针对沙化土地广泛分布的汉江中游河谷平原区，采用MODIsEVI数据分析2003～2011年区域植被状态时空变化，并据此探讨沙化土地的动态特征。利用时序植被指数统计分析，探讨研究区植被的总体变化规律；分析不同缓冲区植被指数的空间分布格局，反映了区域环境状况的空间差异以及由此而可能产生的土地利用格局的变化；并基于不同距离缓冲区的EⅥ时空差异对比分析，探讨沙化土地动态与植被变化的关联关系。研究表明，近9a来汉江中游河谷平原区EVI呈明显上升趋势；随着离河流距离的逐渐增加，每千米范围内各年的年均EⅥ值均表现出先增大后减小的空间特征，并在距河3km区域处EVI值达到最大；而Ew的时空差异，则体现了沙化土地的空间分布与动态特征。

英文摘要：

Remote sensing has the advantage of high temporal resolution and monitoring large scale environment,thus it has been widely used to monitor the dynamic status of desertification. The vegetation index extracted from remotely sensed image can be used for regional desertification assessment. The normalized difference vegetation index （NDVI）,as a common vegetation index, has been widely used to quantitatively and qualitatively assess the desertification during the past 20 years. However, the soil background and atmospheric noise influenced the application of NDVI. The enhanced vegetation index （EVI） is developed to avoid the interference from soil backgrounds and atmosphere, thus may show efficiency in monitoring the desertification dynamism. The plain area in the middle reaches of the Hanjiang River, especially for the valley,is characterized by high coverage. Monitoring the desertification status with regular remote sensing data is difficult, although the desertification of this region is ubiquitous. In this study,the vegetation coverage changes of this region during 2003 2011 were investigated with the time series of MODIS EVI data. The dynamics of desertification decreased during this period, as the EVI increased gradually. The South-to-North Water Diversion Project triggered the decline of groundwater level for middle reaches of the Hanjiang River, and this might facilitate the desertification. Furthermore, the impairment of the decline in groundwater on EVI was negatively correlated to the distance from river. In response,a large area of land afforesting has been initiated to prevent the land from deserting in Lao Hekou,Xiangfan and Zhongxiang since 1990. However, the improvement of this project on vegetable coverage has not been accessed yet. According to the distance from the river, the region investigated was assigned as 8 buffer zones with equal distance of 1 km and the associated characteristics were analyzed. There were pronounced spatial fluctuations for EVI in buffer regions of different distanc