Canopy gap fraction and origin in second-growth forests of Washington County, Ohio

Gaps created by natural mortality of one or a small group of canopy trees are an important fine-scale disturbance event in southeastern Ohio forests. Differences in gap fraction, gap-making species, and the relative importance of several classes of gap origin were examined using transects installed on upper north- and south-facing slopes across the Marietta Unit of the Wayne National Forest. Canopy gap and expanded gap fractions were estimated at 9.37% and 12.10% of total land area, respectively, at the land-scape level. No significant differences in gap fraction between north- and south-facing slopes were detected. The most common mode of gap origin was the tip-up of an individual canopy tree. The frequency of single- and multiple-tree gaps was not found to be correlated with aspect. Oaks (Quercus) constituted the majority of gap-making trees for both north-and south-facing slopes.