OOS 51-8
Getting ahead of the front: Evaluating impacts of emerald ash borer (Agrilus planipennis) on forest vegetation in eastern North America
In North America, Fraxinus comprises six species of native ash, with a combined geographic distribution that coincides with the range of the eastern deciduous forest. All species are susceptible to emerald ash borer (EAB, Agrilus planipennis), an insect that is causing widespread mortality. While similar in severity to previous invasive forest pathogens, like chestnut blight, new technologies allow this disturbance to be mapped across space and time to quantify effects on vegetation. Our primary research question relates to spatial variation of changes in vegetation composition and structure in response to the loss of ash. We utilize the EREN Permanent Forest Plot Project (PFPP), which provides infrastructure for this spatially variable data. At each site, data are collected by faculty and undergraduate students from member institutions according to the PFPP and EAB Impacts Study protocols; on-site meetings and Google technologies are used to enhance interinstitutional communication. Additional variables for this study include extent of tree damage, indicators of EAB infestation, understory community composition, and distribution vectors for the spread of EAB. In Fall 2012, the EAB Protocol was tested in Ohio and Pennsylvania, both within the range of EAB at the time, and released to the EREN community in Summer 2013.
Results/Conclusions
Ash trees continue to show signs of EAB dieback and mortality, but few patterns in vegetation response have emerged given multi-year data from only two sites. Density of mature ash (≥15 cm dbh) is similar (67-71 trees/ha) at both sites, with ash trees composing up to 22% of the overstory. At the northwestern Ohio site, EAB already infested and killed most ash trees, yet blue ash (F. quadrangulata) appears to survive longer than other ash species. While 23% of the mature ash trees at the southwestern Pennsylvania site showed symptoms of EAB infestation, no mortality was observed. Differential light and other resource availability is predicted to result in differences in understory vegetation response. Presence of invasive plant species could also affect the short- and long-term successional trajectory of the forest with the loss of ash. In two different semesters, 25 total students have worked across institutional boundaries to co-present their results through published abstracts and local and regional conferences. Three additional EREN member institutions (Sewanee, SUNY Plattsburgh, SUNY New Paltz) have initiated the EAB Impacts Study, and we continue to recruit member institutions throughout the range of Fraxinus and to share collaborative models for undergraduate student involvement.