The majority of tree growth on the monsoonal Tibetan Plateau has benefited from recent summer warming

Abstract The Tibetan Plateau (TP) is characterized by the world's highest timberlines, largest altitudinal range of forest distribution, and high warming rates. Whether the growth of most forests benefits from climate warming or is inhibited by warming-induced drought stress is still under debate. To understand this question, we collected tree-ring width (TRW) data from 6762 trees at 203 sites that contain 12 genera over the monsoonal TP (MTP) with an elevation range between 975 and 4478 m a.s.l. All sites were equally split into four transects along their altitudinal ranking. The mean tree growth rate (MTGR) of each transect was developed by assembling standardized TRW records. Our results suggest that MTGRs of the upper three transects (2992–4478 m) were stimulated by an increase in the summer (May-September) minimum temperature and have experienced unprecedented high values since the 1980s over the past three to four centuries. In contrast, warming-associated drought stress resulted in a sharp growth drop and minimum MTGR in the lowest transect (975–2970 m) during the 2000s, which was most pronounced in the Himalayan Mountains. We conclude that the majority of tree growth on the MTP has benefited from recent summer warming. The results are robust regardless of using alternative detrending methods, but still could be susceptible to the small replications of some species, outdated end years, oversimplification of the regional climate conditions, and varying growth response within each transect.