Managing understory fagus grandifolia for promoting beech bark disease resistance in Northern Hardwood Stands

Abstract

Many Allegheny hardwood stands contain dense understories of very shade-tolerant American beech, resulting from partial disturbances that have accelerated root sucker development. The low-shade produced by these sprouts hampers silvicultural regeneration efforts to maintain species diversity in new cohorts. An increasing proportion of sprouts result from stressed trees infested with beech bark disease. The clonal sprouts also have a genetic affinity for the disease. A mixture of Accord® and Oust® herbicides, applied to understory vegetation after shelterwood establishment cuts, can significantly reduce understory beech density. Yet, retention of some overstory beech, with demonstrated disease resistance, is ecologically desirable. The root sprouts from these parent trees should also have resistance to the disease. We used broadcast herbicide application to kill understory vegetation after shelterwood harvests in three stands, and tested the effect of herbicide on beech sprouts associated with resistant trees. Eight years after treatment, plots that had received herbicide had similar densities of beech to no-herbicide plots. However, there were significant differences in seedling densities among stands (P = .0303) and species (P = .0014). Our results indicate that there is much temporal variability in regeneration dynamics after treatment. Resistant beech sprouts are still competitive in the long term, even after herbicide application.