Original Paper

Biological Invasions

, Volume 16, Issue 4, pp 859-873

Ash (Fraxinus spp.) mortality, regeneration, and seed bank dynamics in mixed hardwood forests following invasion by emerald ash borer (Agrilus planipennis)

  • Wendy S. KloosterAffiliated withDepartment of Horticulture and Crop Science, Ohio Agricultural Research and Development Center, The Ohio State University Email author 
  • , Daniel A. HermsAffiliated withDepartment of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University
  • , Kathleen S. KnightAffiliated withForestry Sciences Laboratory, Northern Research Station, USDA Forest Service
  • , Catherine P. HermsAffiliated withDepartment of Horticulture and Crop Science, Ohio Agricultural Research and Development Center, The Ohio State University
  • , Deborah G. McCulloughAffiliated withDepartments of Entomology and Forestry, Michigan State University
  • , Annemarie SmithAffiliated withDepartment of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University
  • , Kamal J. K. GandhiAffiliated withDepartment of Entomology, Ohio Agricultural Research and Development Center, The Ohio State UniversityDaniel B. Warnell School of Forestry and Natural Resources, The University of Georgia
  • , John CardinaAffiliated withDepartment of Horticulture and Crop Science, Ohio Agricultural Research and Development Center, The Ohio State University

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Abstract

Emerald ash borer (EAB; Agrilus planipennis) has killed millions of ash trees and threatens ash throughout North America, and long-term persistence of ash will depend on the potential for regeneration. We quantified ash demography, including mortality and regeneration, of Fraxinus americana (white ash), Fraxinus pennsylvanica (green ash), and Fraxinus nigra (black ash) in mixed hardwood forests near the epicenter of the EAB invasion in southeastern Michigan and throughout Ohio. Plots were established across a gradient of ash densities. Ash was the most important species in hydric sites, and ranked second among all species in mesic and xeric sites. In sites nearest the epicenter in Michigan, ash mortality exceeded 99 % by 2009, and few or no newly germinated ash seedlings were observed, leaving only an “orphaned cohort” of established ash seedlings and saplings. As ash mortality increased, the number of viable ash seeds in soil samples decreased sharply, and no viable seeds were collected in 2007 or 2008. In Ohio sites farther from the epicenter, densities of new ash seedlings were much higher in plots with healthy ash trees compared to plots where trees had died. EAB was still present in low densities in Michigan and Ohio stands in 2012 where average mortality of ash was nearly 100 %. The future of ash at these sites will depend on the outcome of the dynamic interaction between the orphaned cohort of previously established ash seedlings and saplings and low density EAB populations.

Keywords

Ash regeneration Demography Invasive forest pest Seedlings