Relationship between vegetation change and extreme climate indices on the Inner Mongolia Plateau, China, from 1982 to 2013

Climate extremes have resulted in substantial vegetation changes during the last several decades, especially in high latitude regions of the Northern Hemisphere. As a climatically-sensitive region, the Inner Mongolia Plateau (IMP) is currently experiencing prominent climate extremes. To identify how climate extremes affect vegetation in the IMP, we calculated 11 indices of climatic extremes for 6 sub-regions of the IMP based on daily maximum and minimum temperature and precipitation. Long intervals of Normalized Difference Vegetation Index (NDVI) derived from the Global Inventory Modeling and Mapping Study (GIMMS), as well as their correlations with climate indices, were investigated at different temporal scales (annual, seasonal and monthly). The results show that on an annual scale, NDVI has the same trend as precipitation extremes and extreme low temperatures, while it has the opposite trend with extreme high temperatures. In contrast, on monthly and seasonal scales, most of the extreme climate indices are significantly positively related with NDVI. In addition, a spatial heterogeneity analysis indicates that the vegetation in desert steppe and steppe desert was relatively less sensitive to the extreme temperature indices in summer, while in general the vegetation in forest and sand desert was insensitive to the extreme precipitation indices in summer. NDVI has a significant relationship with the extreme temperature indices with a time lag of least three months, and with the extreme precipitation indices with a time lag of two months. Finally, our results suggest that extreme climatic events have become more frequent and intense under ongoing global warming.