Local Climatic Factors Mediated Impacts of Large-Scale Climate Oscillations on the Growth of Vegetation Across the Tibetan Plateau

Abstract

Large-scale climate oscillations, particularly the Atlantic Multidecadal Oscillation (AMO) and the Pacific Decadal Oscillation (PDO), have widespread influences on climate systems across the Tibetan Plateau (TP). It is understudied how the temporal changes in AMO and PDO affected growth of vegetation through modifying the local climatic factors in different areas across the TP. We used the AMO and PDO indices, gridded growing season mean temperature (T_GS), cumulative precipitation (P_GS), and normalized difference vegetation index (NDVI_GS) data from 1982 to 2015 to investigate the temporal trends of these variables and the correlations of the T_GS and P_GS with each of the AMO and PDO indices as well as their correlations with the NDVI_GS. The results showed that the warming of the T_GS over the TP and the increases of the P_GS in western, central, and northeastern areas of the TP may have been related to an increase of the AMO index and a decrease of the PDO index. Combining those relationships with the spatial patterns of the T_GS-NDVI_GS and P_GS-NDVI_GS correlations suggested that the changes of the AMO and PDO may have indirectly increased the NDVI_GS in the central and northeastern areas of the TP by increasing T_GS and P_GS, in most parts of the southwestern TP by increasing P_GS, and in the eastern and south-central regions of the TP by increasing T_GS. In contrast, the decrease of the NDVI_GS in some areas of the southeastern and southwestern TP may have been associated with a negative effect of warming as a result of changes in the AMO and PDO. These results highlight the indirect impacts of changes in large-scale climate oscillations on the growth of vegetation through modification of local climatic factors across the TP, and they suggest the substantial spatial heterogeneity of these impacts largely depends on the responses of vegetation to local climatic factors.