Dynamic evolution and driving force analysis of land use/cover change on loess plateau watershed

Using land resources quantity change model and land use/cover change index, dynamic changes and driving forces of land use/cover change were discussed in Tianshui, Gansu Province during the resent twenty years. The results showed that slope farmland area declined sharply, terrace area increased rapidly, forestland area and orchard area increased steadily from 1986 to 2004. According to the change of land-use type transfer, the entering speed of terrace was slightly less than the exiting speed, which was in a state of equilibrium for two-way high-speed conversion, while the entering speed of shrub land was less than the exiting speed, and presented a scale reduced trend. The change degrees of the land use types in the previous period (1986－1995) was much more obvious than that in the later period (1995－2004). Besides special topography and climate factors, national policies, population growth and economic development are driving forces of land use types change. After the implementation of the natural forest protection project and returning farmland to forest projects, land use situation in the region has been improved.