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Background/Question/Methods: Many eastern deciduous forests are changing in species composition and diversity due to a variety of conditions (e.g., canopy closure, non-native invasive species). In this study, between the sample years of 1997, 2009 and 2017, we compared the tree community on the south-facing ridge (15-35% slope) of the old-growth, mixed mesophytic forest at Boone Cliffs Nature Preserve (Burlington, KY), with particular attention to the effects of the emerald ash borer (Agrilus planipennis) on community composition and diversity. In each of those three years, six established circular plots (0.04 ha/plot) that were 30-meters apart were used to measure trees [> 3.5 in diameter breast height (DBH)], with an additional measurement of saplings (3.5 in < DBH ≥ 0.5 in) taken in 2017. Analyses included calculations of Importance Value (summation of density, frequency, and basal area), species diversity, and density and basal area. Results/Conclusions: Overall, we found a minimal decline in tree species diversity, based upon the Index of Species Evenness (J’) (1997=1.7, 2017=1.5), the Shannon-Wiener index of species diversity (H’) (1997=0.68, 2017=0.64), and total richness (1997=12 species, 2017=10 species). Both the tree community density (416 to 450 trees/ha) and basal area (25.8 to 31.4 m2/ha) had increased over 20 years, suggesting both recruitment into the tree class size (>3.5 in DBH) and growth of established trees. However, the community of this south-facing ridge is changing, as the species with the second-highest IV in 1997, the American white ash (Fraxinus americana), has now been fully eliminated by the emerald ash borer [IV: 46.58 (1997), 0.00 (2017)]. In 2017, this community is even more dominated by sugar maple (Acer saccharum) [IV: 106.84 (1997), IV=127.91 (2017)]. The light gaps resulting from ash dieback appear to also be allowing some shade-intolerant species (e.g., Quercus spp., Carya spp., Robina pseudoacacia) to become more important in the community. We anticipate this community to be a Sugar Maple dominated community instead of the Sugar Maple-American white ash community it was in 2009. We hope our study can serve as an example of dynamic trends in similar eastern forests. |
