Community, edaphic, and historical analysis of mixed oak forests of the Ridge and Valley Province, in central Pennsylvania

Using species importance, stands were separated into four groups along detrended correspondence analysis axes one and two. Betula lenta-Quercus prinus-Quercus rubra and Q. prinus-Q. rubra groups occurred on sandstone-based Inceptisols and Ultisols on ridges, whereas mixed-Quercus and Quercus alba groups were representative of limestone-based Alfisols on valley floors. Quercus species dominated the overstory of all groups; however, the understories mainly comprised shade-adapted Acer rubrum, Acer pensylvanicum and (or) B. lenta on the xeric ridges and A. rubrum and Prunus serotina in the mesic valleys. The presettlement forests consisted of Quercus, Pinus and Castanea dentata on the ridges and Quercus, Pinus and Carya in the valleys. Comparisons between presettlement and present-day forests indicate that Pinus strobus and C. dentata have declined dramatically, whereas Quercus species have increased. Changes in disturbance patterns following European settlement initially favored Quercus expansion, followed later by increases in Acer, Prunus and Betula. Under existing conditions where large-scale disturbances from fire or logging are minimal, Quercus species are expected to decline slowly in importance, being replaced by Acer, Prunus and (or) Betula species regardless of site moisture relations. Mixed oak forests do not appear to represent a prominent edaphic climax in the region. -from Authors