The evolutionary value of tree-ring plasticity in Douglas-fir
Climate change threatens forest trees. Their ability to resist depends on their potential to adapt. Phenotypic plasticity, i.e. the potential for individual adaptation, is a rapid mechanism that can allow trees to adjust to new climatic conditions. Tree-rings allow retrospective estimation of phenotypic plasticity of wood formation to climate in forest trees. In this study we show how to estimate linear reaction norms of annual ring variables as a function of climate. We use the slope of the reaction norms as an estimate of phenotypic plasticity of Douglas-fir. We then estimate the variation in phenotypic plasticity between provenances, and relate it to past climate variation in the natural range. We show that there is an individual potential to adapt to climate change in Douglas-fir, that this potential is variable and genetically determined and is related with local adaptation to drought in the species natural range. As a conclusion we show that there is a potential for evolutionary adaptation of phenotypic plasticity of traits related with resistance to drought in Douglas-fir. Whether this potential is enough for Douglas-fir to adapt to climate change remains an open question.