Invasive Emerald Ash Borer (Agrilus planipennis- EAB) has killed hundreds of millions of ash (Fraxinus spp.) trees in North America, including >200 in the 8 ha Chance Creek Nature Preserve (Lorain Co, OH). The deaths affect forest structure by opening canopy gaps that increase light reaching the forest floor, thus altering sub-canopy environments. We previously documented that increased light levels are significantly correlated with increased forb and graminoid abundances, soil moisture, and organic matter. We conducted an invertebrate survey to examine relationships between species diversity and habitat characteristics in upland, slope, and floodplain habitats. Our study sites vary in ash loss – from high-loss plots to sites that lacked ash trees dating to a 1974 survey. In summer 2016, we used 72 pitfall traps to sample diversity and abundances in eight 0.04 ha subplots. We hypothesized that disturbance patterns would drive beetle diversity, and we therefore predicted that beetle taxa would be non-randomly distributed with respect to plot history and disturbance. We used Percent Similarity, Shannon’s diversity index (H’), and the effective number of species (eH’) to compare plots; ANOVA to compare habitat types and beetle distributions; and, Canonical Correspondence Analysis (CCA) to examine relationships between taxa and habitat characteristics.
Results/Conclusions
We report here on 154 beetles from eight genera, and as we predicted, taxa were distributed in a highly non-random pattern (p < 0.0001). Densities ranged from a single Necrophila to 50 Pterostichus. Percent Similarity connected the three sites with the highest disturbance histories, driven by Pterostichus’ disproportionate abundance in the high ash-loss plots. Forbs and graminoids dominated disturbed plots, which had higher average S (4.8 v 3.5; n.s.), higher eH’(3.5 v 3.0; n.s.), and more total beetles (110 v 44; p < 0.05) as compared to undisturbed sites. Abacidus occurred only in disturbed sites, and was associated with Cyclotrachelus and Pterostichus in the CCA where they were correlated with bare ground and woody debris. Necrophila and Chaelinus were most closely related to % organic matter and forbs. The greater taxonomic diversity, higher effective number of genera, and greater total numbers in disturbed habitats indicate a feedback between beetles and plant diversity that require further explorations. Given that the peak of local ash deaths occurred in 2009, we have the opportunity to document changes that will improve our understanding of forest responses to the invasive EAB.