Comparing assisted migration seed sources of two oak species in a Minnesota red pine woodland

Forest assisted migration (FAM) is the movement of tree species or genotypes to habitat believed to be characterized by the climate of the source population. FAM can be an integral component of climate adaptation projects. An example of such a project is the Red Pine Adaptive Silviculture for Climate Change (Red Pine ASCC) experiment in northern Minesota, USA. The experiment includes planting seedlings of northern red oak and bur oak from two different seed sources south of the study area. The primary source for both species was central Minnesota, one seed zone south of the local zone. However, due to the number of seedlings needed, a secondary source was also used that included red oak from southwest lower Michigan and bur oak from eastern Iowa. Known planting locations and densities of the seed sources allowed comparison of survival and growth to assess if the primary seed sources out-performed the secondary sources. For both species, densities after five growing seasons were not significantly different between seed sources, suggesting similar survival. Heights and diameters of bur oak were nearly identical for the two seed sources, suggesting similar growth rates. For northern red oak, seedlings of the Minnesota seed source were significantly taller and larger in diameter than the Michigan seed source, but differences were small. Our results suggest managers can be opportunistic when acquiring seedlings of these species for similar FAM projects.