Study on the dynamic changes of land desertification in Yulin Prefecture, northwestern China based on RS and GIS

With taking many measures of combating land desertification in the past decades, the distinct effects have been achieved in Yulin Prefecture of Shaanxi Province in northwestern China. The objective of this study was to monitor and analyze the dynamic changes of desertification in the regions in the 14 years from 1986 to 2000 using remote sensing and geographic information system (GIS), so as to derive the useful references for the restraining land desertification and the further fathering sandy land in the future. According to the surface landscape indices, the sandy land was divided into four types, such as shifting sandy land, semi-shifting sandy land, semi-fixed sandy land and fixed sandy land, and the desertified land had been divided into light level desertified, moderate level desertified, severe level desertified and heavily level desertified corresponding. The data of sandy land in these two dates were interpreted and obtained by interpreting the images of TM in 1986 and 2000 with the visually interactive interpretation. The data of dynamic changes of reversing from sandy land and desertified land were obtained by overlaying databases in these two periods. The study results show that there was 29,523 ha of newly deserified land occurred, and most of the newly desertified lands are heavily severe desertified grades. At the same time, 104,896 ha of desertified land were rehabilitated. As a result, the desertified decreased by 75,373ha kept a stable reversed situation as a whole during the 14-year periods.