Impact of variations in vegetation on surface air temperature change over the Chinese Loess Plateau

摘要

Studying the drivers and combating the effects of climate change is more urgent than ever, particularly in regions with limited water and sensitive ecosystems. This study evaluated the effect of vegetation variation on surface air temperature (SAT) change in the Chinese Loess Plateau over 1982-2015 based on the 'observation minus reanal-ysis' (OMR) method. Observed temperature, ERA-lnterim reanalysis temperature, and Global Inventory Modeling and Mapping Studies normalized difference vegetation index (NDVI) 3rd generation were used to analyze the relationship between OMR temperature (representing vegetation impact on SAT) and NDVI. Results showed that the Loess Plateau, especially its central-east areas, has undergone a rapid increase in NDVI and rapid decrease in OMR temperature during 1982-2015. This implies a strong cooling effect of vegetation restoration on SAT change. The mean annual NDVI (M_NDVI) and NDVI trend (SlopeNDVI) were negatively correlated with OMR temperature trend (Slope_OMR.) on the Loess Plateau (P< 0.001). However, the relationships between M_NDVI (S/ope_NDVI) and Slope_OMR varied among the arid, semi-arid, and semi-humid regions. As a result, the impacts of restoration of vegetation condition on SAT change during 1982-2015 were estimated to be 0.04, -0.01, and -0.07 ℃ decade-1 in the arid, semi-arid, and semi-humid regions, respectively. For the entire Loess Plateau, the restoration of its vegetation condition led to a cooling effect of -0.02 ℃ decade~-1 during 1982-2015 and a cooling effect of -0.05 ℃ in the period following the implementation of the Grain for Green Project (GGP). Moreover, among the three major land use types of the Loess Plateau (i.e., grassland, farmland, and forest), vegetation restoration of forest demonstrated the most obvious cooling effect (-0.06 ℃ decade~-1 during 1982-2015). These results are the first quantitative estimation of the impact of vegetation variation on SAT across the entire Loess Plateau, and demonstrate the ecological effect of afforestation efforts in the southeastern areas in terms of climate warming alleviation.