Resistance of forest community types to structural and compositional change following beech bark disease infestation

Pathogens change forest composition and structure by selectively eliminating susceptible individuals and species. Caused by a complex between an exotic scale insect and fungi, beech bark disease has infected mature American beech (Fagus grandifolia) trees through most of the species range. Before succumbing to the disease, infected trees generate root sprouts, transforming beech from a dominant canopy species into an abundant subcanopy species. Root sprouting can create dense beech thickets that interfere with the regeneration of other species. Exclusion of species from the understory has ecological and economic implications. This study compared forest CQmmun..ity types for their resistance to CQmpositional and structural change from beech thickets. The expansion and density of beech sprouts, as well as the density of other species in the thickets were measured in seven different forests in central Maine. Mixed hardwood forests, specifically an ash-birch-maple forest, tend to be most resistant to change, while a hemlock-pine-oak forest was least resistant. This information may be useful for managers to prioritize forest community types in which to control beech thickets.