Ecological and hydrological impacts of the emerald ash borer on black ash forests

This project examines the ecological and hydrological impacts of emerald ash borer on black ash-dominated wetlands throughout the Lake States using large-scale experimental studies documenting impacts of black ash mortality on ecosystem processes, wildlife communities, and evaluating potential mitigation and adaptation strategies under future climate and invasion scenarios.  Adaptation strategies being evaluated include the planting of non-host tree species and management techniques to increase levels of compositional and structural complexity within these systems.  Work is also generating maps of the distribution of black ash forest habitats to help prioritize areas for conservation and mitigation in the context of emerald ash borer impacts.

Analyses of four-year trends in survival of planted seedlings indicate that American elm, swamp white oak, and hackberry have had the greatest levels of survival out of the 11 non-ash species planted (> 80% survival for all three species).  Of these, swamp white oak and hackberry are not currently present in this portion of the region, but are projected to have suitable climate conditions in these areas over the next 100 years. Survival of planted lowland conifer species, including northern white cedar and black spruce, has been greatest in areas where an ash canopy is still present, namely the group selection (harvest of 0.1 acre gaps across stand) and EAB-mortality treatments (girdled plots) highlighting the negative impacts clearcutting may have on our ability to establish non-host species in these areas. Moreover, survival of northern white cedar has been greatly limited by elevated levels of herbivory in these areas, underscoring the importance of accounting for other stressors when developing adaptive approaches. The fourth season of post-harvest hydrological measurements indicated that clearcut and girdle treatments continue to contain flooded conditions that persisted six to eight weeks longer than in no-harvest and group selection areas.  These results indicate that EAB-induced mortality and associated presalvage harvesting activities will cause dramatic shifts in groundwater dynamics that could limit the effectiveness of planting non-host species once EAB is affecting an area, particularly if early growing season rainfall patterns increase.  This work has been expanded to black ash forest systems in Michigan and Wisconsin to better characterize EAB impacts and possible adaptation strategies.  This includes quantifying the impacts of ash mortality on herpetological and insect communities beginning in summer 2015 as well as developing a managers guide for adaptive managementin these systems.