Climate-induced changes in the stem form of 5 North American tree species

Generally, the effects of climate change on tree growth focus on changes in one dimension of a tree. However, diameter increment along the main stem reacts differently to climatic variables, which in turn influences tree form. These differences can thus have important implications on stem volume, which could induce biases in future forest biomass estimation. A stem taper model including climatic variables was fitted to stem analysis data of five different species (Abies balsamea, Betula papyrifera, Picea glauca, Picea mariana, Populus tremuloides) distributed along a gradient from the temperate to the boreal forest of Eastern Canada. The effects of shifts in stem form on tree volume between different climatic scenarios were then estimated and related to different functional traits. Changes in stem form with climatic variables were observed for four of the five species, with up to 5% differences in stem volume between different climatic situations. Changes in stem volume were found to decrease with increasing waterlogging and shade tolerance. The most important differences in stem volume can induce changes of 3-4% in the biomass of a single tree. Not taking into account shifts in stem form could have implications in forest biomass estimations.