The emerald ash borer (EAB) invasion has resulted in the deaths of hundreds of million ash trees in North America since the1990s. The consequences for forest community changes are far-reaching, and are in the early stages of investigation. One important change is the creation of large canopy gaps that allow for significant increases in sunlight reaching the forest floor. This increase in light and exposure can alter herbaceous vegetation, with subsequent influence on seedling establishment and woody plant growth. We hypothesized that the rapid increase in light will favor herbaceous vegetation before recovery by woody plants. We therefore predicted that increased light levels will be positively correlated with forb and graminoid cover. In September 2016, we recorded digital images of 165 one-meter2 quadrats located in the corners and center of each of 33 permanent plots, and used ImageJ to quantify percent cover for six categories: forbs, graminoids, woody plants, vines, bare ground, and litter. We recorded hemispheric photos directly above each quadrat and used WinSCANOPY to estimate the percent open canopy. We used a one-tail Mann-Whitney to compare high ash-loss vs. low ash-loss quadrats, and Pearson’s correlation coefficients between light levels and each of the ground cover categories.
Results/Conclusions
We found a highly significant difference (p < 0.001) in percent open canopy between high ash-loss (mean = 16.1%) and low ash-loss plots (mean = 7.6%). Percent open canopy was positively correlated with both high forb (r = 0.40, p < 0.0001) and graminoid (r = 0.55, p < 0.0001) densities. We found no significant correlations with woody vegetation, vines, bare ground, or litter. These results are consistent with our predictions. This baseline of information provides a basis for subsequent sampling and analyses. We will repeat surveys throughout the spring and summer 2017 to monitor spring ephemerals and fern distributions. We will also compare the high ash-loss plots with plots not associated with ash loss, but that are naturally well lit, such as on forest edges and exposed slopes. Surveys over the next several years will allow us to record how this forest recovers.