Dong Yu-xiang

Sandy desertification status and its driving mechanism in North Tibet Plateau

As the main body of Qinghai-Tibetan Plateau, North Tibet Plateau is one of three major sandy desertification regions in China and also a representative sandy desertification zone of Qinghai-Tibet Plateau. Accordingly, it is an important region for the study of recent sandy desertification processes and formation mechanism. From such aspects as desertified land types, areas and distributions etc., this paper analyses in detail the sandy desertification status on North Tibet Plateau, and qualitatively and quantitatively deals with the main factors that affect recent sandy desertification processes and the driving mechanism. Research results show that North Tibet Plateau is an important sandy desertification region in China characterized with large desertified land areas, diversified types, high severity, extensive distributions and serious damages. Sandy desertification occurrence and development resulted from combined effects of natural factors, anthropogenic factors, natural processes and man-made processes, of which climatic change is the main driving force.

Present status and cause of land desertification in the Yarlung Zangbo River basin

The Yarlung Zangbo River basin is a spacial zone in the south of Xiang, the types, distribution and causes of desertified lands have special features. The type, area, distribution and damage of desertification land in the Yarlung Zangbo River basin are firstly analysed in detail by using latest investigation information. According to the classification criteria of desertified land types and grades, the desertified land in the Yarlung Zangbo River basin can be divided into three grades and five types: fixed sand (dune) land, semi-bare sand and gravel land, semi-fixed sand (dune) land, base sand and gravel land, and shifting sand (dune) land. The desertified lands in the basin are mainly distributed in the widevalley floor and tributary junction area. The main factors affecting desertification are fragile eco-environment, climate warming and drying and over-exploitation of land resources. The man-made factors leading to desertification in the Yarlung Zangbo River basin are over-cutting and over-grazing, dominated by over-grazing.