Abstract
Otindag Sandy Land, located in the Xilingol grassland in Inner Mongolia, exemplifies the significant increase in grassland degradation in recent years, which has drawn attention as a source of dust storms in the Beijing-Tianjin area. This study carried out a detailed investigation in order to clarify the vegetation changes and their causes. First, the normalized difference vegetation index （NDVI） during the growing season（April to October）, derived from long-term satellite data sets （AVHRR/GIMMS ［1981-2006］ and MODIS/TERRA ［2000-2014］）, was used to estimate changes in the amount of vegetation. The April-October integrated NDVI value as an indicator of annual vegetation amount was used to examine the vegetation temporal-spatial change in interannual variability and long-term change. Then, using the Otindag Sandy Land temperature and precipitation data within 10 observation points, we examined their impact on the variation of NDVI values. We took April-October cumulative NDVI values as purpose variables and temperatures and precipitation as explanatory variables, and subjected them to multiple regression analysis. Finally, a change in livestock numbers as well as the anthropogenic impact of afforestation in Xinlinhaote were examined to ascertain their effects on NDVI values.The results revealed that the NDVI change did not present a clear increase and decrease tendency during the 34-year period, but a low value tendency was seen after 2003. The multiple correlation coefficient R of the NDVI measured value, and the predicted value was very high at 0.91. The effects of livestock were not directly related to the interannual vegetation variance;however, when drought occurred during a cattle population increase, it revealed that the vegetation amount decreased sharply.
