Data from: Climatic stress during stand development alters the sign and magnitude of age-related growth responses in a subtropical mountain pine

The modification of typical age-related growth by environmental changes is
poorly understood, In part because there is a lack of consensus at
individual tree level regarding age-dependent growth responses to climate
warming as stands develop. To increase our current understanding about how
multiple drivers of environmental change can modify growth responses as
trees age we used tree ring data of a mountain subtropical pine species
along an altitudinal gradient covering more than 2,200 m of altitude. We
applied mixed-linear models to determine how absolute and relative
age-dependent growth varies depending on stand development; and to
quantify the relative importance of tree age and climate on individual
tree growth responses. Tree age was the most important factor for tree
growth in models parameterised using data from all forest developmental
stages. Contrastingly, the relationship found between tree age and growth
became non-significant in models parameterised using data corresponding to
mature stages. These results suggest that although absolute tree growth
can continuously increase along tree size when trees reach maturity age
had no effect on growth. Tree growth was strongly reduced under increased
annual temperature, leading to more constant age-related growth responses.
Furthermore, young trees were the most sensitive to reductions in relative
growth rates, but absolute growth was strongly reduced under increased
temperature in old trees. Our results help to reconcile previous
contrasting findings of age-related growth responses at the individual
tree level, suggesting that the sign and magnitude of age-related growth
responses vary with stand development. The different responses found to
climate for absolute and relative growth rates suggest that young trees
are particularly vulnerable under warming climate, but reduced absolute
growth in old trees could alter the species’ potential as a carbon sink in
the future.