IMPLICATIONS OF EMERALD ASH BORER DISTURBANCE ON BLACK ASH WETLAND WATERSHED HYDROLOGY, SOIL CARBON EFFLUX, AND DISSOLVED ORGANIC MATTER COMPOSITION

Recently, emerald ash borer (EAB) (Burprestidae: Agrilus planipennis) has been introduced as a non-native, invasive pest to ash (Fraxinus spp.) forests in Northeastern North America. The rapid and extensive expansion of EAB populations is considered an important ecological and economic disturbance as it has the potential to decimate existing ash stands throughout North America. It is unknown how EAB-induced removal or suppression of the major overstory component in black ash wetlands will affect water table fluctuations and export of gaseous and dissolved carbon. The major objectives of this study were to characterize water and carbon cycling conditions in undisturbed wetlands, and to evaluate the effect of a simulated EAB-disturbance on wetland water tables and soil carbon fluxes in black ash wetlands. An EAB infestation was simulated by girdling and felling all black ash trees greater than 2.5-cm diameter, and environmental conditions were compared during pre- and post-treatment study periods. Black ash wetland water tables in the Ottawa National Forest were persistently connected to and regulated by regional groundwater. Mean-annual water table positions were sensitive to inter-annual weather variability. Water tables were significantly higher during the growing season, soil CO2 emissions were significantly larger, and large soil CH4 emissions occurred more frequently in disturbed study sites. The relative magnitude of wetland water table and gaseous soil carbon emission (CO2 and CH4) response to disturbances were mitigated by connections to regional groundwater. EAB-induced alterations to site hydrology is not likely to alter future natural re-vegetation processes in the absence of black ash, and therefore their ecological significance as forested wetlands on the landscape is expected to remain intact