GIS-based study on spatial-temporal changes of land use in Wuding River Basin in the 1990s
20世纪90年代无定河流域土地利用的时空变化

Regional land use change is an important part of global change. The Wuding River Basin, located in the middle reach of the Yellow River, is characteristic with high sediment load in less water. Since the 1950s, various conservation measures have been adopted throughout the basin, including vegetation (trees, bushes and grasses) plantting, sand shifting control, terracing, reservoirs and dams construction, and so on. These measures have changed the underlying surface greatly. Based on Landsat TM images data in the 1990s, we analyze the spatial-temporal changes of land use of Wuding River Basin using GIS and statistic methods. The results show that the land use changed greatly in the Wuding River Basin in the 1990s. In the first five years, cultivated land, forestland and un-used land decreased obviously while grassland increased. In the second five years, the situation was reversed, grassland increased and cultivated land, forestland and un-used land decreased. During the ten years, cultivated land and un-used land reduced, at the same time, forestland and grassland increased. The rate of land use change in the first five years is higher than that of the second five years.The major change types were cultivated land turned to forestland and grassland, and un-used land converted into cultivated land and grassland. In the first five years, the rate of the land use change in the study was up to 0.85%. The changing rates of un-used land and grassland were higher, being 3.2% and 1.94% respectively. While, in the second five years, the rate of the regional land use change was 0.3%. The changing rates of forestland and un-used land were 2.75% and 1.71% respectively. Finally, we also come to the conclusion that there are obvious spatial differences in land use changes. For forestland change, the Nalin, Lu and Dali sub-basins were greater. Glassland and un-used land changes mainly occurred in Yuxi and Hailiutu sub-basins. Conservation measures and socio-economic development were the direct causes for land use change in the Wuding River Basin.