HISTORICAL VARIATION IN FIRE, OAK RECRUITMENT, AND POST-LOGGING ACCELERATED SUCCESSION IN CENTRAL PENNSYLVANIA

Composition, structure and radial growth patterns were studied in relatively undisturbed, mature mixed-oak (Quercus), valley floor forests and in similar forests extensively logged between 1936-1946 in central Pennsylvania. These data were analyzed in relation to presettlement forest composition and historical fire records to investigate temporal variation in Quercus recruitment versus accelerated succession of more shade tolerant species following logging. Presettlement valley floor forests in the study area were dominated by Quercus alba and Pinus strobus. Recurring logging and fire between 1780-1900 associated with charcoal iron furnace activity increased Quercus and decreased Pinus dominance in second-growth forests established during that period. Between 1908-1989 the total area burned by wildfire throughout Pennsylvania decreased by > 99% (from > 400,000 ha to < 3500 ha per year). The decreased influence of logging and fire this century facilitated recruitment of later successional Acer and Prunus species in Quercus forest understories. Logging of forests in this condition rapidly accelerated the rate of obtaining canopy dominance for A. rubrum, A. saccharum and P. serotina in area forests. This form of disturbance-mediated accelerated succession should be anticipated in a wide variety of forest types with an overstory dominated by early successional species and an understory comprised mainly of later successional species.