Improving the Composition of Beech-Dominated Northern Hardwood Understories in Northern Maine

Abstract

Abstract The natural regeneration that develops following the shelterwood and selection harvesting of northern hardwood stands across the Northeast is often plagued by an overabundance of American beech infected with beech bark disease. This regenerating beech typically dominates and interferes with the regeneration of more desired hardwood species (sugar maple, yellow birch, and red maple), lowering the productivity and value of future stands. We tested factorial combinations of glyphosate herbicide (Accord Concentrate) rate and surfactant (Entrée 5735) concentration to identify an optimal treatment that would maximize beech control while minimizing sugar maple injury. Third-year posttreatment results revealed that glyphosate rate was a more important factor than surfactant concentration in reducing beech abundance and preserving sugar maple. The optimal treatment (0.56‐1.12 kg/ha of glyphosate plus 0.25‐0.5% surfactant) selectively removed 60‐80% of beech stems, whereas sugar maple control was less than 20%. The five dominant hardwood species differed substantially in their susceptibility to the treatments in the following decreasing order: beech > striped maple > yellow birch > red maple > sugar maple. Similar results produced using a backpack mistblower suggested transferability of treatment effects to operational applications using a tractor-mounted mistblower. Our findings indicate that this relatively low-cost and effective treatment can substantially improve the understory composition of northern hardwood stands.