Divergent growth between spruce and fir at alpine treelines on the east edge of the Tibetan Plateau in response to recent climate warming

摘要

The divergent responses of trees to climate warming including their increasing/diminishing growth coherency have been reported at treeline in some circumpolar north areas and the Alps regions. However, it is unclear how the radial growth of treeline trees on the Tibetan Plateau responds to climate warming. We totally collected 534 ring cores of spruce (Plcea spp.) and fir (Abies spp.) genera from 17 sites on the east edge of the Tibetan Plateau. The pairwise correlations between the ring width indexof all trees in a population were analysed before and after the rapid warming, respectively, and the correlations between individual tree growth and monthly mean temperature were accordingly studied. The proportions of trees positively correlated with spring and growing season temperature were also counted. The results showed that the growth coherency of the trees decreased for both spruce and fir, but the coherency of the correlation between individual tree growth and monthly temperature decreased onlyfor fir. The proportion of spruce positively responding to the spring and growing season temperature increased while that of fir did not change, except for those in the wetter sites. The spatial variability of trees’ response to the spring and growingseason temperature coincided with the precipitation decrease. The results indicate that higher spring and growing season temperatures are beneficial for the radial growth of spruce but could cause drought stress to fir. We conclude that drought stress induced by climate warming may drive the divergent responses and the spatial variability for trees on the east edge of the Tibetan Plateau.