Elevation-dependent tree growth response to recent warming and drought on eastern Tibetan Plateau

Increasing warming and drought intensity and frequency have led to profound impacts on forest ecosystems around the world. However, few studies have assessed the impacts of climate change on the alpine forests of different tree species at the regional scale on the eastern Tibetan Plateau (TP). We established 40 standard tree ring width chronologies based on 2137 cores from 1161 trees for five conifer species on the Gannan Plateau, located in eastern TP. Climate data from CRU grids are employed to study the relationships between radial growth and climate factors at each site during a common period of 1961–2019. A mixed-effects model is used to disentangle the relative contributions of elevation and species on the relationships between tree radial growth and climatic variables. The results highlight that tree growth responses to climate varied between species, which mainly results from species distribution being determined by elevation. Specifically, tree growth at higher elevations is mainly constrained by low temperature in the growing season, while drought is the controlling factor limiting tree growth at lower elevations. Moreover, elevation plays a more important role in determining the tree growth response to climate than species. The radial growth of Picea purpurea and Abies fargesii at higher elevations might benefit from future warming due to a positive correlation with temperature in the growing season, which might promote an upward shift in species distribution. While increasing warming and drought intensity may restrict tree growth of Picea asperata, Picea wilsonii, and Pinus tabulaeformis or even cause tree mortality at lower elevations, this may lead to future species composition changes and distribution range constriction.