Adaptation to climate change: Genetic variation is both a short- and a long-term solution

We propose a methodology combining a biophysical site index model and a seed source transfer model based on both temperature and precipitation to estimate white spruce plantation yield under present and future global warming conditions. The biophysical site index model predicts dominant height at 25 years, which is further used to estimate plantation yield using yield tables. The transfer model shows that, on average, seed sources are best adapted to the temperature conditions where they presently grow, and give maximum yield under these conditions. However, this model also shows that transfer of seed sources to drier sites could improve plantation yield. To predict site index values under climate change conditions, values obtained from the biophysical site index model are corrected by a factor estimated using the seed source transfer model. Our simulation results predict that global warming should favour a slight increase in white spruce plantation yield in southern Quebec. However, one cannot expect to obtain similar yields from a seed source rapidly exposed to warmer conditions compared with a seed source that is presently growing under climatic conditions to which it has become adapted. It would take several generations (adaptation lag) for a seed source to adapt to warmer conditions. We believe that the method we propose will be helpful in identifying the most productive seed source to be used at any given location in the province, and in revising seed source transfer rules.