中文摘要：

本文从地表植被时空变化和土壤水分时空变化两个不同的方向入手,分析了黑河中游8个完整区县2000年-2009年的绿洲化和荒漠化过程。研究表明,2000年-2009年间,山丹、民乐、酒泉肃州区中部、肃南的东部及甘州-临泽绿洲区一直是黑河中游植被分布的重点区域;从植被角度分析,虽然黑河中游各区县均有零散分布的植被退化区,但总体而言植被状况在逐渐变好,其中民乐县和山丹县的植被状况最好,变化最明显;从土壤水分状况分析,肃南、山丹和民乐3个地区的土壤水分状况要好于其它地区,这与它们所处的地理位置、降雨量和土地利用状况有关。

英文摘要：

The Heihe River basin is the second largest inland river basin in the arid region of northwestern China,showing a typically fragile ecology and the environment.Under the combined effect of the water resource distribution and human activities,great changes in land use and surface characteristics across the region have occurred.Desertification and oasification are two major opposite trends in land use.In general,vegetation and soil moisture can be taken as indicators of desertification and oasification.In this paper,processes of desertification and oasification in the middle reaches of the Heihe River were analyzed on the basis of spatial-temporal information regarding vegetation and soil moisture derived from satellite imageries,with the objective to examine where and what the degree of land use change occurred,which would be helpful for gaining an improved understanding of the ecology and the hydrologic cycle in ecologically fragile areas.Normalized Difference Vegetation Index（NDVI） time series of 16-day composite MOD13A2 data products and Temperature-Vegetation Dryness Index（TVDI） values calculated by daily MYD11A1 data products were used to explore overall changes in vegetation and soil moisture conditions during the last decade,respectively.Mean values and slope of ordinary least squares（OLS） regression line and covariance of NDVI and TVDI were computed to assess the processes of desertification and oassification.Results showed that since 2000,Shandan and Minle characterized by crop and woodland,the middle of Suzhou by crop,the east of Sunan by grass,and Ganzhou-Linze oasis by crop were found to be densely vegetated.Although there was some degraded land,the vegetation cover generally increased as a whole.The best vegetated areas were distributed primarily in Shandan and Minle where marked variations in vegetation exhibited during the recent 10 years.As for the conditions of soil moisture,Sunan,Shandan,and Minle appeared to be better than other counties.The soil moisture condition was primarily dete