Classification System for Desertification and Its Quantitative Assessment Methodology in China

Based on the desertification definition of United Nations Convention to Combat Desertification and features of desertification in China, three-level hierarchical classification system for desertification and quantitative assessment methodology of desertification degree were developed and used to evaluate desertification danger degree across the country. The system is composed of three components: type of desertification, type of land utilization and degree of desertification. The type of desertification monitored in China was divided into 4 major categories, 15 sub-categories and 52 types. Vegetation coverage, soil characteristics, and topography are considered as three major indicators for quantitative assessment of desertified land. A simple, yet practically sound mathematical assessment model was built using these indicators. Furthurmore, a regional land desertification warning model was also constructed on the basis of the ratios of non-desertified land area to desertified land area in different degrees. The warning result of wind-erosion desertification at county scale for 12 provinces in northern China was also calculated by this model.

Characteristics of Desertification Change in Lake Basin Area in Gangcha County

Qinghai Lake Basin area in Gangcha county is selected as the study area in terms of desertification change features in this paper.Based on the remote sensing(RS)and global positioning system(GPS)technologies,the desertification information range from 1989 to 2014 in the study area is extracted.Using the method of the decision tree,the desertification in the research area is been divided into four grades including mild desertification,moderate desertification,severe desertification and serious desertification.The change characteristics of desertification in the study area were analyzed in detail,which showed that the desertification in the study area experienced a process of first development and then a reversal.The rapid development of desertification appears in the 1990s,where about 1101.22 kilometers of desertification area was increased in this stage.Since the twenty-first Century,the desertification is gradually significant recovered and local area exist intensified desertification.There are tendencies of interactive transform in different types of desertification.The tendencies of different degrees of desertification land are rising,and there’re some differences in rising rates,where the expansion rate of moderate desertification is the biggest,increasing by 7.27 kilometers per year.