Abstract: Land desertification is one of the serious problems in environmental degeneration and has been paid a great attention to. By taking Longyangxia Reservoir area of Qinghai Province as the study area, in this paper, a dynamic monitoring of land desertification in this area is carried out by means of remote sensing (RS) and geographical information system (GIS). The results show that land desertification occurs extensively in the reservoir area, its area occupied 71.5% of the total in 1996, in which the areas of seriously desertified land, strongly desertifying land, desertifying land, and potentially desertifying land occupied 10.9%, 1.3%, 10.3% and 49% of the total respectively. Land desertification is becoming more serious, and the area of seriously desertified land enlarged for 189 km² within 10 years. The overall trend of land desertification develops towards a positive direction although a reverse occurs in partial area. During the period from 1987 to 1996, the areas evolved from strongly desertifying land, desertifying land and potentially desertifying land to seriously desertified land in the reservoir area were 71.27, 83.51, and 83.89 km² respectively, and the areas reversed from seriously desertified land to these three kinds were 12.13, 10.53, and 22.90 km² respectively during the same period.

Key words: land desertification, remote sensing, geographical information system