基于MODIS数据的柴达木盆地南缘绿洲土地覆盖动态变化研究

Land Cover Change of Southern Fringe Oasis in the Qaidam Basin from 2000 to 2009 Based on MODIS Data

基于遥感和GIS技术手段,利用2000—2009年生长季的MODIS数据对柴达木盆地南缘绿洲进行了土地覆盖分类,得到前期(2000—2004年)和后期(2005—2009年)两期土地分类图以及2000—2009年土地覆盖类型变化趋势图,分析了2000—2009年10 a尺度上该地区土地覆盖类型的面积变化以及空间分布格局。分析得知,柴达木盆地南缘绿洲同时存在两种演化趋势:绿洲化和荒漠化。近10 a来绿洲化的总面积为1 040 km2,占研究区面积的4.58%,主要集中在荒漠化区域与稳定区域之间;荒漠化的总面积为399 km2,占研究区面积的1.76%,其中80%集中在绿洲边缘(4 km以内),也就是说,绿洲的边缘地区相对于绿洲的其他区域更易于发生荒漠化现象。从整个研究区来看,绿洲化趋势高于荒漠化趋势,其原因可能主要是由于近年来气候变暖,昆仑山上大量冰雪融化,为下游绿洲提供了一定的水资源,但绿洲上游一些地区人类活动的加剧使用了大量的水资源间接地影响了绿洲的演化,使得绿洲边缘水资源缺乏的地区荒漠化加剧。

Base on MODIS data of the growth season from 2000 to 2009 and GIS technology,this paper carried out a land cover classification of southern fringe oasis in the Qaidam basin and obtained land classification maps during 2000—2004 and 2005—2009,then the dynamic change of land cover types and its spatial pattern was analyzed.There are two dynamic trends of land cover change,oasification and desertification,in the study area.The area of oasification zone is 1 040 km^2,accounting for 4.58% of the study area,which is mainly located between desertification zone and stable zone.In contrast,the area of desertification zone is 399 km^2,accounting for 1.76% of the study area,and 80% of the desertification zone is located near oasis（within 4 km）.That is,the marginal area of oasis is more easily ready for degradation than the inner area.The trend of oasification is more significant than that of desertification in the whole study area mainly because of climate warming.Climate warming leads to ice and snow melting on the Kunlun Mountains and enhances water availability in the downstream part of the oasis.However,the aggravation of human activities in the upstream part of oasis results in more water consumption and leads to serious water shortage and desertification near oasis margin.