The decline of northern hardwoods is currently attributed to a broad spectrum of factors—ecological, physical, and anthropogenic. We analyzed changes in seedling and sapling densities in northeastern forest communities to understand how the cumulative effects of multiple stressors on tree regeneration may affect future composition. Beginning in 2002, data of seedlings and samplings were collected in Permanent Forest Inventory (PFI) plots at Cornell’s Arnot Experimental Forest. At each PFI plot, we established two to four seedling and sapling subplots, and counted the number of seedling and sapling stems at each of the subplots. Each quarter-acre PFI plot had two to four seedling and sapling subplots within its perimeter. Eighteen plots originally established between 2002 and 2006 were resampled during 2013 through 2015 to document changes in per-hectare seedling and sapling species densities after 11(± 2) years. We also compared our data to inventory results from 1985 to 2008 at a set of adjacent plots to observe patterns over a longer period of time. Combining data from both time periods, 1985-2008 and 2002-2015, allows for analysis of both long-term and short-term trends in seedling and sapling density.
Results/Conclusions
In our short-term observations from 2002 to 2015, we found a decrease in seedling densities of American beech (Fagus grandifolia), red oak (Quercus rubra), striped maple (Acer pensylvanicum), and Sugar Maple (Acer saccharum), and an increase in seedling densities of Birch (Betula spp.) and Red Maple (Acer rubrum). Sapling densities of each species generally followed the same pattern as seedlings, except in the cases of American beech and sugar maple saplings, which showed increasing densities. Long-term (1985-2008 vs. 2002-2015) results showed similar trends, except in the cases of A. rubrum and Betula, which exhibited decreasing sapling densities from 1985-2008. Our results suggest that diverse northeastern hardwood forests may be replaced by homogenous beech thickets in the short term if current trends continue, which could have negative implications for ecosystem health and biodiversity.