The invasive emerald ash borer ( Agrilus planipennis ) is a threat to all North American ash (genus Fraxinus ) trees, but wetland ecosystems dominated by black ash ( F. nigra ) are of particular concern to land managers. The rapid and extensive death of black ash on the landscape causes unprecedented ecological and hydrological impacts to cascade through the ecosystem. A strategy to combat such impacts and maintain these wetlands as forested is to underplant these stands with seedlings of alternative species that are capable of maturing into canopy trees. This study planted seedlings of seven non-ash tree species in black ash wetlands across northern Michigan and Wisconsin and assessed the factors that have the greatest effect on seedling survival and growth. First year survival across all species was 54 %, and by two years after planting total survival was 47 % with a mean relative growth rate of 5.47 cm/yr. The best-performing species in terms of both survival and growth rates were river birch ( Betula nigra ), silver maple ( Acer saccharinum ), and swamp white oak ( Quercus bicolor ). Bur oak ( Q. macrocarpa ) and red maple ( A. rubrum ) also exhibited high rates of survival despite having below average growth rates. The main factors influencing seedling performance were hydrology and microtopography, with greatly increased survival for seedlings planted on higher microsites further from the water table. Insufficient natural regeneration of canopy species observed in the understory of all stands warrants planting within these systems to avoid the vegetative community shift to dominance of herbaceous or shrub species. • Two years after planting, black ash stands had insufficient natural regeneration. • Black spruce had the lowest survival and growth rates of the planted species. • Hydrology and microtopography had the most influence on seedling performance. • It is important to consider multiple goals when designing planting initiatives.
Davenport et al. (Sat,) studied this question.