Alaska yellow-cedar (Callitropsis nootkatensis) is currently under threat from climate change.

Yellow-cedar relies on persistent winter snowpack to keep its roots from freezing during the winter. Due to climate change, the snow that normally blankets much of southeast Alaska and British Columbia is disappearing. This results in massive die-offs of yellow-cedar, called yellow cedar decline. My research focused on whether there might be local variation in the freezing tolerance of yellow-cedar - in other words, if some populations might be more likely to survive snow loss and the subsequent root freezing.

Why does yellow-cedar grow where it does?

Where a tree grows depends on both large-scale, regional factors and small-scale factors that can differ within meters of each other. When we look at the large-scale factors, we normally consider climate models (temperature, precipitation, snow, etc.) and topographic factors (how the landscape is shaped). Small-scale factors can vary, but my project looked primarily at light level and species composition.

One problem we often run into when we’re trying to model a species range is not having enough data - we need specific locations that we know have yellow-cedar over hundreds of miles, and one scientist can’t cover that in a summer area. To get around this, we often try to use community science resources like iNaturalist - it’s a great way to get good data about a species. However, we don’t have a good idea of what biases exist in datasets like these. One of my projects involved evaluating this bias using a collection of species distribution models based on different datasets, to understand the uncertainty present in this type of data source.