| 摘 要： |
Land surface greening has substantially changed the carbon sequestration and hydrological processes over Tibetan Plateau (TP). Previous studies have revealed that the increased total precipitation (P-total) is the main driver of the enhanced peak growth in TP. However, the role of precipitation pattern, especially the frequency of precipitation (P-freq, number of rainy days [>0.1 mm]), has not been well analyzed. We used time series of satellite-derived Normalized Difference Vegetation Index (NDVI) to investigate the effect of P-freq in controlling the peak growth (the maximum of the NDVI [NDVImax]) of different vegetation types in TP for the period of 1982-2015. We found that the widespread greening trend with P-total disappeared when P-freq was introduced as a controlling variable, and that P-freq alone contributed more than P-total to the increase of NDVImax. The underlying mechanism for the higher contribution of P-freq than P-total to NDVImax is that increased P-freq significantly improved soil moisture, reduced daytime temperature while increased nighttime temperature, thereby alleviating summer drought. Our results highlight the importance of P-freq in interpreting the variation of peak growth, and these effects might be better represented in ecosystem models by considering P-freq rather than P-total alone with future climate change. |
在线留言
联系我们
所长信箱