Swarts, Kelly - Tree Ring Genomics

Research

Kelly Swarts standing outside next to a pine tree with snow in the back; she has long brown hair and a black sweater onPhoto: Johan Gunséus

How do conifers adapt under climate change?

Conifers are ecologically dominant and economically important, but are globally succumbing to drought, disease, early-budding and other challenges. One of the oldest lineages on earth, conifers have the genetic diversity to adapt to a broad range of environments. However, long generation times combined with the greatly increased rate of climate change globally challenges trees’ ability to adapt, resulting in weakened individuals and eventually stand loss.

We use quantitative, computational and population genetic approaches in forests across Europe to understand climate adaptation in conifers. To understand how trees adapt to their environment – and how they might perform under changing climate – we first need to understand how much of growth is due to genetics and how much can be attributed to the experienced environment. By focusing on annual growth measured from tree-rings, which form when growth stops during the winter months in temperate regions, we can observe individuals growing across their lifespan. For the years with available environmental data from historical records, weather stations or satellites, we can model individual environmental responses, which are often highly heritable.

Close-up of a cross-section of a tree stem showing tree rings; a red jagged line is placed on top the tree ring photo illustrating the avarage growth during different years starting from before 1950 to 2020Many trees today are struggling in the face of changing climate. This increment core from a Norway Spruce (Picea abies) tree growing in Berchtesgaden, Germany has seen a decline in growth over the last few decades.

Once we have estimates of adaptation for individuals, we can parse the genome to understand the genetics underlying adaptation, and how this may differ across species and populations. We can also generate predictive models to estimate how well adapted an individual might be to an environment that it hasn’t experienced. Because we are working with tree-rings, we are not limited to controlled populations. This means that we can evaluate any tree’s performance in any modeled environment. As environments shift under climate change, this approach provides a powerful tool to select parents for healthy, resilient forests.

Schematic overview about the work flow for doing tree ring genomics

Our work is funded by generous support from: