Changes in seedlings' composition and abundance following soil scarification and amendments in a northern hardwood forest

A combination of global changes (e.g., soil acidification, invasive species, forest management, climate) impacts the regeneration dynamics of sugar maple-dominated stands in northeastern North America. More specifically, there are concerns about the regeneration of sugar maple and other high-value species due to the expansion of American beech and its bark disease, killing mature trees, compromising fiber supply and other ecosystem services. Here, we set up a field trial to study the effect of soil scarification, amendments (nitrogen fertilization, liming, and wood ash), and their interactions, on tree species establishment following understory vegetation removal in a beech-invaded sugar maple stand to promote the establishment of high-value species (i.e. sugar maple and yellow birch), to control beech regeneration, and help reduce the impacts of beech bark disease on stand development. After four years of monitoring, we found that maple-beech stands with well-drained soils were promising sites for the success of sugar maple and yellow birch establishment. Soil scarification had a limited effect on sugar maple and beech establishment while it enhanced that of yellow birch, pin cherry and red maple. The combination of soil scarification and amendments was more effective in promoting the recovery of yellow birch and pin cherry and controlling the recovery of beech and red maple than their separated effects. Lime amendment promoted sugar maple establishment without favouring competitors such as yellow birch, pin cherry and red maple, and limited beech establishment. Overall, our results suggest that combining soil scari-fication and amendments on targeted site types could help fine-tune tree establishment conditions in northern hardwood forests.