Remediation and Recovery of Forests in the Great Lakes Region Following Emerald Ash Borer Infestation and Competitive Terrestrial Invasive Plants

Ash trees have a significant ecological and economic role across North America. They are a valuable lumber product and have significant cultural value to many Native Americans communities. Specifically, the black ash species is highly prized for basket making by the many tribal members across the Great Lakes region. However, one of the most unique features of ash is their ability to grown in lowland ecosystems. Across the Great Lakes region, black and green ash species are vital in swamp and bottomland hardwood forests, respectively. They regulate water table levels, and the accompanying plant community, such that without ash trees, forested wetlands would convert to open canopy wet meadows dominated by grasses and shrubs. 

Emerald ash borer (EAB), an Asian wood-boring beetle first introduced to North America near Detroit, Michigan, in the early 2000s, now threatens more than 2.1 billion ash trees and their respective ecosystems. Once introduced to an area, EAB can cause 99 percent ash mortality and dramatically alter ecosystem functions of lowland forests. These wetlands may also experience permanent changes in community structure, such as altered age class structure and changes in the understory which have implications for wildlife habitats.

Managers are investigating methods to mitigate the impact of EAB destruction of ash forests, but it is very unlikely that reforestation with ash will be a viable treatment option due to poor regeneration and chance of reinfestation. One management strategy that addresses several of the foundational functions that ash perform is to plant replacement tree species. The replacement species will have to survive the dramatic seasonal temperature fluctuations of the upper Great Lakes region and flooding for at least part of the growing season. If planted post-EAB, seedlings will also have to compete with understory vegetation such as the highly competitive Eurasian genotypes of reed canary grass. 

Objectives

Test the use of a single application of imazapyr herbicide applied to reed canary grass and other competing vegetation, followed by hand planting of appropriate tree species to restore forests decimated by emerald ash borer. Develop best management practices to reforest lowland stands in the Great Lakes Region following ash forest devastation by emerald ash borer.

Expected Results

Outputs

Information on stand characteristics important when selecting tree species for reforestation of lowland sites. Knowledge of effectiveness of a single herbicide treatment in reducing the competitive capacity of invasive reed canary grass and facilitating tree seedling survival and growth.  A decision matrix tool to assist foresters in making decisions on tree species selection. Operationally feasible management strategies to assist foresters with the task of maintaining lowland areas in the Great Lakes Region as forested ecosystems.

Expected Outcomes

Forest managers have operationally feasible management strategies to restore forests in lowlands and swamps in the Great Lakes Region following emerald ash borer infestation.  Prevention of site conversion to wet meadows that would reduce critical habitat for many wildlife species.

Metrics of Success

Restoration of forests in lowland areas of the Great Lakes Region following devastation of ash forests due to emerald ash borer.

Geographies and High-Risk Landscapes to Be Addressed

Regional

This work is focused on swamp and bottomland forests dominated by ash species in the Great Lakes region that have been devastated by emerald ash borer infestations.