Twenty Years of Change (1997-2017) in an Old-growth Forest Community at Boone Cliffs Nature Preserve (Burlington, KY)

Indianapolis, IN

Many eastern deciduous forests are changing in species composition and diversity due to a variety of conditions. In this study, using three sample years (1997, 2009 and 201)7), we compared the tree community on the south-facing ridge of the mixed mesophytic, old-growth forest at Boone Cliffs Nature Preserve (Burlington, KY), with particular attention to the effects of the emerald ash borer (EAB) (Agrilus planipennis). In each year, six established circular plots (0.04 ha/plot) at 30-meters apart were used to measure trees [> 3.5 in diameter breast height (DBH]. 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 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 been eliminated by EAB [IV: 46.58 (1997), 0.00 (2017)]. In 2017, this community is more dominated by sugar maple (Acer saccharum) [IV: 106.84 (1997), IV=127.91 (2017)], while light gaps resulting from ash dieback appear to be allowing shade-intolerant species (e.g., Quercus spp., Carya spp., Robina pseudoacacia) a greater importance in the community. We hope our study can serve as an example of dynamic trends in similar eastern forests.