[Dynamic changes of land use and landscape patterns in middle reaches of Shule River, Northwest China]

By using the MSS images in 1976, TM images in 1989 and 2010, and ETM+ images in 2000, in combining with GIS and landscape ecological methods, this paper analyzed the changes of land use/cover and landscape patterns in Yumen County at the middle reaches of Shule River from 1976 to 2010. In the study period, the major patterns of land use change in the County were the conversions from grassland and Gobi to farmland, from farmland to construction land, and from grassland to Gobi. Such a land use change underwent a process of 'slow - tremendous - obvious', during which, the landscape density increased, the largest path index decreased after an initial increase, the weighted area index increased, and the landscape shape became irregular. In the meantime, the nearest distances between patches and the separation among different patches decreased, the patches became more complex, and the landscape diversity and evenness increased after an initial decrease. The increased landscape diversity and fragmentation also showed that the land uses became more complex. The growth of agricultural population and the development of economy were the most direct driving forces of the land use/cover change in Yumen City, whereas the climatic and policy factors also had important effects on the land use change in the study area.