Changes in ash tree demography associated with emerald ash borer invasion, indicated by regional forest inventory data from the Great Lakes States

Abstract

The emerald ash borer (EAB) ( Agrilus planipennis Fairmaire) is a nonnative phloem-feeding beetle that was accidentally introduced near Detroit, Michigan, two to three decades ago. North American ash ( Fraxinus spp.) exhibit little or no resistance, and as this insect species expands its range, extensive mortality results. Previous studies of the impacts of EAB, typical of most insect and disease impact studies, utilized data acquired from sites with known infestations and cannot be used to make regional estimates of change on forest land. By contrast, this study investigated the regional impacts of EAB on the affected resource using information from a large-scale forest inventory (Forest Inventory and Analysis program of the US Department of Agriculture, Forest Service) previously implemented to estimate regional forest resources. Results indicate that since 1980, ash has been increasing throughout many of the Great Lakes States but EAB is reversing this trend in recently invaded areas. Within 50 km of the epicenter of the EAB invasion, a major decline was observed after 2004. For growing stock (trees at least 12.7 cm diameter at breast height), average ash volume decreased from 12.7 to 3.2 m3·ha–1and mortality increased from 0.1 to 1.4 m3·ha–1·year–1on timberland between the 2004 and 2009 inventories.