Emerald ash borer (EAB) (Agrilus planipennis) is a buprestid beetle native to Asia that was accidentally introduced to North America in the mid-1990s. It has spread to ten US States and two Canadian provinces, killing millions of ash (Fraxinus spp.) trees. The effects of EAB on forest ecosystems are being studied through a collaborative research program involving USFS NRS-02 and Ohio State University. In over 250 monitoring plots in forests in Ohio and Michigan, representing a gradient of EAB infestation duration, we are monitoring the decline and mortality of thousands of ash trees, the responses of both native and invasive plant species, changes in species composition and forest structure, and effects on other organisms and ecosystem processes. The plots are located in forest stands of different ages and in different habitats to include all five ash tree species native to the region (F. Americana, F. pennsylvanica, F. nigra, F. profunda, and F. quadrangulata). Yearly monitoring began in 2004 and continues to the present. This monitoring plot system represents a wealth of data, and subsets of these plots have been used to study carabid beetle community composition, woodpecker feeding, seedbanks, EAB population dynamics, effects of past land use, and EAB parasitoids.
Results/Conclusions
Our research has resulted in several key findings. Mortality of mature ash trees in a forest stand may reach 98% within six years of infestation by EAB, and is not affected by the density, basal area, or species composition of ash trees. In areas that have been infested the longest, only 0.8% of mature ash trees remain alive, while many seedlings and approximately 30% of saplings are alive. EAB persists at low densities in these stands. Invasive plant species are present in most plots, however, their percent cover is generally low. These plants may increase in abundance due to canopy gaps that result from ash mortality. EAB may cause a cascade of effects on other species in these forest ecosystems. Woodpecker feeding behavior changes as woodpeckers take advantage of the abundant food source that EAB represents. Species composition and abundance of litter-dwelling carabid beetles change as gaps form. Native parasitoid wasp species have been observed parasitizing EAB in central Ohio. We will continue to monitor these changing forest ecosystems as the effects of EAB reverberate through them.
