Increased exotic invasive plant response to natural disturbance and elevated deer populations

Remnants of Hurricane Isabel damaged forest canopy in a pre-existing one hectare research plot in Maryland in 2003. Roughly 25 percent of the tree canopy was damaged or destroyed by wind. Patterns of change of native and exotic plant abundance and species richness were studied to determine the response of plants in the herbaceous layer to this natural disturbance. Exclosed (fenced) and open vegetation plots were constructed to determine the role of preferential herbivory by white-tailed deer in invasion.Exotic plants increased significantly in species richness and abundance after the hurricane. The increase in exotic plant abundance was greater than that of native plants. There was no significant relationship between higher initial native plant diversity and reduced exotic plant invasion. These results fit in a continuum of diversity-invasibility studies in which the diversity-invasibility relationship changed from negative at small scales to positive at large scales. Preferential herbivory decreased native plant abundance and increased exotic plant abundance. Results suggest that fencing to reduce deer browse may be more effective than herbicide treatment at controlling exotic plants.