Emerald Ash Borer (Agrilus planipennis) has had a detrimental impact on all species of ash (Fraxinus spp.) in the Eastern United States. It is possible that ash trees may be completely lost. Thus, it is necessary to understand what impact the loss of ash trees is having on forest composition. In this study, plant species composition was examined surrounding dead ash trees and compared to random areas within the forest. This study took place at Moraine Nature Preserve in Valparaiso, Indiana where Emerald Ash Borer first appeared in 2006. Dead canopy reaching Fraxinus spp. were randomly found throughout the preserve, and these were compared with random sites located under intact forest canopy. These random sites were 20 meters away from the ash sites using a random compass direction. Plant species composition was determined within a 2 m radius circle extending from the dead ash trees. At the random sites, a circle with the diameter of the previous dead Fraxinus spp. were excluded. Plant species composition/count and invasive plant composition/count were then determined in a 2 m radius around the circle. Statistical analysis was done using a Mann-Whitney U Test for the number of invasive species underneath dead Fraxinus spp. versus random sites in the forest. Additionally, species diversity and canopy cover was calculated.
Results/Conclusions
Invasive plant species were significantly more abundant underneath dead ash versus other areas in the forest (Mann-Whitney U, p < 0.001). There were 116.6% more invasive species underneath ash than random areas with Berberis thunbergii and Rosa multiflora. However, there was no difference in species diversity between the dead ash trees and random sites (p > 0.05). Additionally, Fraxinus spp. make up the majority of tree seedlings/saplings underneath the ash trees and the correlating random sites. Further study should be done to determine if canopy gaps are aiding in the establishment of invasive species, or if more light is just aiding in growth and reproduction in areas where they are already established.