Effects of prescribed fire on Quercus rubra regeneration near its northern range limit

Northern red oak ( Quercus rubra ) is predicted to expand northward in the northeastern United States with climate change and could increase functional diversity of northern forests. However, red oak regeneration currently faces many challenges including herbivory, pathogens, and consequences of forest mesophication such as light insufficiency and competition with more mesic species. Prescribed burns may address some of these challenges to oak recruitment and establishment. In the White Mountain National Forest in New Hampshire, we studied pairs of stands harvested within the past decade, with one stand in each pair receiving a prescribed burn of low-moderate intensity. We surveyed and measured naturally regenerated oak seedlings along transects over two years. Seedling density in burned stands was three times the density in paired unburned controls. Seedlings in burned stands had larger root collar diameters, greater extension growth, and more leaves, likely due to greater light availability in burned stands. Additionally, in a mesocosm experiment, seedlings grown in burned soil developed faster and had thicker root collars by the end of the first season than those grown in unburned soil, suggesting additional soil-mediated benefits. Our study demonstrates positive effects of burning for red oak regeneration via both aboveground and belowground mechanisms and affirms prescribed fire as a potentially beneficial silvicultural management tool for northern red oak at and near its northern range limit. However, in stands where advance regeneration of oak is lacking, a single prescribed burn may not be sufficient to regenerate mature oaks without additional silvicultural intervention. • Prescribed fire promoted Quercus rubra establishment beyond thinning effects alone. • Burning reduced light competition, which enhances oak seedling density and growth. • In a mesocosm experiment, burned soil biology may have benefited oak seedlings.