LUCC of a watershed on the northern Chinese Loess Plateau during 1978-2011

Soil erosion on the Chinese Loess Plateau is most serious over the world. Since the 1950s, a large scale of soil and water conservation measures (including the Grain-for-Green project since 1999) aimed at reducing soil erosion rates has been implemented on the plateau, significantly altering the land use pattern of the region. Based on satellite images, we studied the land use / cover changes (LUCC) of Huangfuchuan watershed, which lies on the northern Loess Plateau, between 1978 and 2011 in terms of land-use dynamic degree, land-use transfer matrix and land use degree, and briefly discussed the driving forces of LUCC. Results showed that (1) grassland is the dominant land use type between 1978 and 2011, accounting for 70%-80% area of the watershed. Unused land accounts for about 9% of the total area , followed by cropland(5.8%) and sand land(4.7%), and the area of other land use types was much smaller (i.e. water body, woodland, residential area). (2) During 1987-2011, the grassland area experienced the trend of decreasing first and then increasing. Although the proportion of grassland area slightly changed, the absolute area is still quite large given its original large occupation .the area of residential land increased In the entire period. the area of unused land, sand land, and cropland increased first and then decreased, and the area of other land use types fluctuated through the study period. (3) Before 2000 , grassland, cropland, unused land and sand land were frequently converted to one another. Grassland was mainly converted to cropland and unused land. Residential land and woodland were mainly transferred from grassland and cropland. The increase in cropland was mainly a result of the conversion from grassland, water body, unused land, and sand land; The reduction of cropland mainly became grassland. The area of sand land and unused land has increased significantly, mainly as a result of the shrinkage of grassland. After 2000, the decrease in grassland area was mainly due to the transfer of unused land, sand land and cropland. (4) land use during 1978-1990 and 1995-2006 was at `the stage of development', while land use during 1990-1995 and 2006-2011 was at `the stage of adjustment or recession'. Overall, there was a considerable LUCC in the Huangfuchuan watershed between 1978 and 2011, and such changes are spatially and temporally various. They are mainly driven by a variety of forces, which varies over time and space, including the governmental policies, soil and water conservation practices, economic development, population growth and climate change.