[Landscape structure of desertification grassland in source region of Yellow River]

This paper analyzed the spatial pattern and its characteristics of different landscape types on the desertification grassland of Maqu County in the source region of Yellow River, based on the principles of landscape ecology, with the help of GIS techniques, and by using landscape heterogeneity indices (landscape diversity and dominance) , landscape isolation indices (patch density and fragmentation), and shape indices (elongation index and fractal dimension). The results showed that on the whole, the landscape structure of this region was simple, but varied locally. Natural landscapes such as grassland, marsh and shrubs were the main body of landscape change. The regional landscape patches had a ribbon shape spatial distribution, and the differences were significant among subregions. From fluvial terrace to low hillsides and alpine grassland, the landscape patch type, landscape diversity, and landscape fragmentation degree decreased gradually, and the landscape structure presented a simplification trend. Desertification landscape, and mobile dune in particular, had great impact on landscape structure, playing an important role in the increment of landscape heterogeneity and fragmentation. Fixed sand lands, semi-fixed sand lands, and potential sand lands had different influences on regional landscape composition and its changes. Compared with desertification landscape, artificial landscape had less effect on landscape structure, but exhibited a wider potential variation range. These two types of landscape would be the dominant factors affecting the landscape structure changes of this region in the future.