Abstract:

Functional traits are usually used to predict plant demographic rates without considering environmental contexts. However, previous studies have consistently found that traits have low explanatory power for plant demographic rates. We hypothesized that accounting for environmental contexts instead of focusing on traits alone could improve our understanding of how traits influence plant demographic rates.

We used generalized linear mixed-effect models to analyse the effects of functional traits (related to leaf, stem, seed and whole plant), environmental gradients (soil nutrients, water and elevation) and their interactions on the survival dynamics of 14 133 saplings and 3289 adults in a 9-ha old-growth temperate forest plot.

We found that environmental variables, neighbour crowding and traits alone (i.e. main effects) influenced plant survival. However, the effects of the latter two variables varied between saplings and adults. The trait–environment interactions influenced plant survival, such that resource conservative traits increased plant survival under harsh conditions but decreased survival under mild conditions. The elevational gradient was the most important environmental factor driving these effects in our plot. Our results support the hypothesis that functional traits influence plant survival depending on environmental contexts in local communities. These results also imply that one species with limited trait variation cannot occupy all environments, which can promote species diversity.

Key words: demographic rates, functional traits, local communities, soil nutrients and water, temperate forest, trait–environment interaction