Aeolian Desertification and Its Landscape Pattern Change in the Zoige Basin,Qinghai-Tibet Plateau during 1975-2005

The development of aeolian desertification from 1975 to 2005 in the Zoige Basin was identified by using remote sensing data and geographic information system method.Remote sensing data used in this study included Landsat multi-spectral scanner(MSS) images of 1975 with spatial resolution of 80 m,Enhanced Thematic Mapper(ETM) images of 2000 with resolution of 30 m,and Thematic Mapper(TM) images of 1990 and 2005 with resolution of 30 m.Result showed that the aeolian desertification land increased rapidly from 1975 to 1990,and it was stable between 1990 and 2000,and decreased slightly from 2000 to 2005.Furthermore,landscape software Fragstats 3.3 was used to analyze the landscape pattern of aeolian desertification land in the Zoige Basin.It was found that fixed sandy dunes(sandy land) and semi-fixed sandy dunes(sandy land) were the main landscape types of aeolian desertification land.The landscape pattern changed significantly,and both the number and the mean patch size of aeolian desertification land patches increased rapidly from1975 to 1990.The fragmentation degree of aeolian desertification land decreased slightly from 1990 to 2000,but it increased from 2000 to 2005.