Composition Shifts, Disturbance, and Canopy-accession Strategy in an Old-growth Forest of Southwestern Ohio, USA

摘要

Forest composition can shift through time in response to a variety of factors including changes in climate conditions and disturbance regimes. In many forests of eastern North America, oak (Quercus) populations are decreasing while maple (Acer) populations are increasing. Altered fire regimes over the last century are thought to be the primary driver of oak-to-maple dynamics; however, other factors may be playing an important role in this dominance transition. Our study sought to determine the community structure and disturbance history of an old-growth forest remnant in an area of western Ohio where fires were historically infrequent. To determine community structure, abundance of woody species was measured within 32 plots at four canopy strata. Dendrochronology was used to determine the disturbance history of the site and canopy accession patterns of canopy trees. We found that oaks and hickories (Carya) were important contributors to the forest canopy, but were less numerous than maples in sub-canopy layers. There was vastly higher biomass of standing dead material from oaks than from other genera. We propose that a cohort of oak and hickory dominance was initiated by a change in historical disturbance regime, and that in recent decades the stand is responding to a suite of multiple interacting ecosystem drivers, which have favored maple regeneration. In the coming decades, this forest, along with others in the region, will be faced with a new suite of interacting drivers including exotic insects, invasive plants, and climate change.