Planning for the future: assessing potential impacts and management options for invasive forest pests at the Offield Nature Preserve.

Abstract

Invasive forest pests are having profound effects on the composition and structure of forests across North America and in some cases management can help to mitigate some of the impacts of these disturbances. We studied the composition and structure of the northern hardwood forest at the Offield Family Nature Preserve in northern Lower Michigan to evaluate the likely impacts that Emerald Ash Borer and Beech Bark Disease will have on the forest. We focused our analysis on two stands, one beech (Fagus grandifolia) dominated and one with a significant white ash (Fraxinus americana) component. Both stands had a large component of susceptible species in the canopy layer, and also had an understory dominated by beech and sugar maple (Acer saccharum). Due to variation in canopy structure and dominance the disturbance will create larger gaps in the beech-dominated stands. However, the disturbance in both stand types is likely to reduce canopy species diversity and resilience to future disturbances such as subsequent pest outbreaks. The currently ash dominated stands will likely transition to almost complete sugar maple dominance, while the beech=dominated stands will potentially undergo a transitional phase of dominance by small beech stems before also becoming sugar maple monocultures. We outline potential management strategies that could be implemented to attempt to combat these trajectories, which include combinations of seedling planting, understory clearing, and overstory thinning or salvaging. We suggest a management regime based around planting and understory clearing, with targeted overstory thinning designed to promote establishment of a diversity of canopy species including some with intermediate shade tolerance.