Trees move. During storms, such as the tornado this past Thursday, ebbing and swaying with the right balance of rigidity and flexibility helps prevent certain tree species from falling to unfortunate deaths. We’re all familiar with this sort of tree movement. But did you know that over long time horizons and successive generations, tree species often move vast distances, to track with changes in climate?
Before looking into how the tree species of Minnesota are set to change over time, let’s take a brief look into their current composition. Minnesota tree species can be divided into two major groups, “temperate” and “boreal,” reflecting the biomes these trees originate from. Currently, boreal trees dominate the colder expanses of Northern Minnesota and up through Canada. Most boreal trees are evergreen, enabling them to photosynthesize in colder climes during more of the year than deciduous trees. In the milder climates of southern Minnesota, on the other hand, temperate trees, which are mostly deciduous, are often able to outcompete conifers adapted to colder climates.
In a 2015 paper, a research group at the University of Minnesota predicted how changes in climate would affect the movement of tree species in Minnesota. To track with warming temperatures making northern areas milder, this paper predicted that temperate species would move northward, and consequently boreal forests in northerly parts of Minnesota would see an increase in temperate specie composition.
Since we’re located in Southern Minnesota, the arb is largely populated by temperate, deciduous trees such as maples, oaks and ash, but there are quite a number of boreal species as well, such as the spruce and pine. If temperatures increase as predicted, the Arb managers are going to have to determine whether they are going to direct conservation efforts to reflect the changing climate, or preserve the past species composition of the arb. In all likelihood, the relative percentage of deciduous trees in the Arb is going to increase, and conservation efforts are going to reflect that change in species composition.