Conifers are ecologically dominant and economically important, but are succumbing to drought, disease, early-budding and other challenges globally because the climate has changed so that mature trees are no longer adapted to their environment. If we could predict how individual tree genotypes would respond to different environments, we could — given environmental predictions — plant the right tree in the right space to ensure healthy forest under changing climate. While over the past century people there has been extensive work in developing experimental plots that allow researchers to understand how trees grow outside of their home environment, these trials are expensive, limiting the genetic diversity that can be evaluated, and take decades to mature. In this project, we are developing a method for quickly estimating adaptive responses to different environments for any forest tree. The key to our proposal is a unique aspect of tree physiology, tree-rings, which result from the cessation of growth at the end of the grouping season, and provides a record of tree growth across its lifespan. We sample this annual growth with tree increment core samples, minimally invasive 5mm biopsies from a tree trunk, which simultaneously provide DNA for genotyping and annual growth measurements, estimated from growth rings. Because there is substantial variation in environment between years, this allows us to partition the sources of growth variation into generalizable environmental responses for years with historical weather or biotic information, using quantitative, genomic and ecological approaches to control for correlated responses. We can then use these estimates to understand the genetics underlying adaptation to environment, and to predict the most suitable individuals for a given location. As environments shift under climate change, this approach will provide a powerful tool to maintain healthy, resilient forests.
