Classification and Successional Changes of Mixed-Oak Forests at the Mohn Mill Area, Pennsylvania

摘要

A vegetation study was conducted within cential Pennsylvania's Ridge and Valley Province at the Mohn Mill natural area, an area that harbors the federally endangered northeastern bulrush, Scirpus ancistrockaetus. A non-metric muitidimensional scalingordination identified two gradients oi species replacement distinguished by differences in forest canopy species and groundcover. Basal-diameter histograms for red maple (Acer rubrum), eastern hemlock (Tsuga canadensis), and witch hazel (Hamamelis virginiana) showed distributions indicative of populations recruiting new individuals, whereas basal-diameter distributions for white oak (Quercus alba), chestnut oak (Q. montana), and red/black oak (Q. Jubra/Q. velutina) indicate declining populations with limited recruitment. Consequently, as current populations of overstory oaks age and ultimately die, they will be replaced by red maple and eastern hemlock. This transition has major implications for herbaceous plants, including the persistence of the northeastern bulrush, given that ground-level light levels will decrease due to the denser canopies of red maple and eastern hemlock recruits.