干旱区生态环境知识资源中心

Desertification in China has become one of the most serious ecological and social problems. The four mega-sandy lands (Hulunbeir, Horqin, Otindag, and Mu Us) in Inner Mongolia are reported to be the most widespread and seriously desertified areas in China.

To explore changes of vegetation activity and the possible driving forces in the four mega-sandy lands over the last three decades.

We investigated spatiotemporal variations in the growing-season (May-September) normalized difference vegetation index (NDVI) and their relationships with climate factors and human activities during 1982-2011, using two NDVI datasets from Global Inventory Modelling and Mapping Studies (GIMMS) and Moderate Resolution Imaging Spectroradiometer (MODIS).

We found a significant overall NDVI increase in Mu Us, but no such trends in the other three. A significant increase was in south and northeast Mu Us and southeast Horqin, and a decrease in south Hulunbeir, northwest Horqin, and central Otindag. NDVI trends were positively correlated with precipitation and uncorrelated with temperature and wind speed in all sandy lands except Mu Us.

NDVI trends showed a large spatial heterogeneity in the four sandy lands. Precipitation was a major determiner for the interannual variations and spatial patterns of NDVI at regional scale, whereas human activities were the cause of NDVI variations at local scale. The consistent interannual variations between two NDVI datasets of GIMMS and MODIS for all four sandy lands suggested that GIMMS NDVI was appropriate for investigating long-term vegetation changes in sandy lands.