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Emerald Ash Borer Invasion: Potential Consequences for the Vassar Ecological Preserve

Elaine Cheung, Vassar College ’13

Professor Dr. Meg Ronsheim

Agrilus planipennis, also known as the Emerald Ash Borer (EAB), is an invasive beetle introduced from Asia that feeds upon and subsequently kills all species of ash trees (Fraxinus sp). The first sightings of EAB in Dutchess County were reported in March 2012. The EAB is likely to have a large impact on the Vassar Ecological Preserve because there are high densities of ash in five areas of the Preserve. The death of ash trees caused by EAB creates large gaps in the forest canopy, affecting the species growing in the forest understory and raising questions about future forest regeneration. Canopy gaps can be filled by the growth of neighboring trees or saplings.  However, invasive plants, such as oriental bittersweet (Celastrus orbiculatus), can also take advantage of these high light areas, outcompeting native species and creating an impenetrable tangle of vines.  I set up nine long-term sampling sites to examine how the loss of ash will affect forest structure and soil composition on the Preserve. Three of the sites were ash-dominated, three were bittersweet-dominated, and the remaining three were dominated by black cherry (Prunus serotina), a native tree that may replace ash trees. Soil cores, canopy photos, and tree and canopy measurements were taken at each site. Nutrient availability was significantly lower in ash vs. black cherry and bittersweet sites, suggesting that soils in currently ash-dominated sites will experience a shift in nutrient composition with the invasion of EAB.  Canopy light levels were highest in the bittersweet-dominated sites.  If bittersweet outcompetes black cherry in the new canopy gaps, high light levels will be maintained, facilitating further bittersweet growth and reducing the biological diversity of the area by preventing the growth of native plants.