基于多时相遥感影像的浑善达克沙地沙漠化监测

沙漠化是浑善达克沙地面临的主要环境问题.为了揭示该地区沙漠化过程,特别是其最新状态,利用1987年和2000年的Landsat TM/ETM 及2006年的中巴资源卫星CCD数据,在地面考察资料及地理信息系统(GIS)的支持下,提取了固定沙地、半固定沙地、流动沙地、丘间草原及湿地5种地表覆被类型,建立了浑善达克沙地沙漠化数据库.结果表明浑善达克沙地在过去20a里发生了沙漠化,但是可分为两个阶段.第一阶段从1987年到2000年,为沙漠化快速发展期,固定沙地面积显著减少,而半固定沙地和流动沙地则明显增加;第二阶段从2000年到2006年,为沙漠化缓减期.尽管发生了沙漠化,但固定沙地仍然是浑善达克沙地面积最大的类型.针对流动沙地的空间变化检测表明在过去20a里沙地恶化的面积远远大于逆转的面积,并且已经形成了几条流动沙带,这意味着浑善达克沙地沙漠化的遏制是一个长期的过程.

Monitoring sandy desertification of the Otindag Sandy Land based on multi-date remote sensing images

Sandy desertification is the main ecological problem the Otindag Sandy Land at present.In order to reveal the process of land degradation,especially the latest situation of sandy desertification,a method integrating remote sensing,Geographic Information System(GIS) and field survey was employed to build a sandy desertification dataset for analysis.Remote sensing images included the Landsat Thematic Mapper(TM) in 1987,the Enhanced Thematic Mapper plus(ETM ) in 2000,and the Charge Coupled Device Camera(CCD) of China-Brazil Earth Resource Satellite(CBERS) in 2006.Five land-cover classes,including active sand dunes,fixed sand dunes,semi-fixed sand dunes,inter-dune grassland and wetlands,were identified.Results showed that the Otindag Sandy Land has been suffering sandy desertification since 1987 with two different desertified stages.First stage from 1987 to 2000 is a serious sandy desertification period,characterized by the fixed sand dunes decreasing at a high speed,and the semi-fixed and active sand dunes increasing remarkably.The second stage spanned from 2000 to 2006 and the sandy desertification was weakened greatly.Although a large area of fixed sand dunes transformed to other types,it is still the dominant type in the Ointdag region at 2006.Spatial change detection based on active sand dunes showed that the area of expansion is much larger than that of reversion in the past two decades,and that several active sand belts have been formed.It suggests that sandy desertification controlling of the Otindag Sandy Land will be a long-time task.