Analysis on Desertification Dynamics based on Remote Sensing and GIS in Zone along the Great Wall in Northern Shaanxi Province

The study area, a part of the southern Mu Us Sandland, is located along the Great Wall in northern Shaanxi Province. Based on database of desertification dynamics from 1986 to 2000, the changes of the sandland were analyzed. The results show that the desertified land had decreased 735\^1 km~(2) from 1986 to 2000 and keep stable reversed situation as a whole. The reversed lands are mainly semi-fixed and semi-shifting sand lands. At the same time, the desertification of arable land, grassland and forest land became very severe. Further, the extremely severe decertified land covers the majority among the increased decertified lands. In the past 14 years, the reason of land desertification being reversed is that a series of positive sand-control measures and governmental policy have been adopted. Nevertheless, land resource is still in desertification process because of unreasonable agricultural practices, heavy livestock grazing and firewood cutting, and the disharmony between coal-mine-resources exploitation and environmental protection.