Patterns of Disturbance in Some Old‐Growth Mesic Forests of Eastern North America

Abstract

To characterize the disturbance regime of one type of vegetation, study areas in which relatively small—scale disturbance predominates were chosen in several old—growth mesic forests in the eastern United States. Canopy openings covered 9.5% of total land area. New gaps were formed at an average of 1% of total land area per year; old gap area closed at a similar rate primarily by sapling height growth. With increasing gap size, vegetation within gaps increased in woody species diversity, total basal area, and total number of stems. Stems also showed accelerated growth into larger size classes. As gaps aged, stems grew into larger size classes and basal area increased. Species responses to canopy gaps varied. Some species survived and became established in fairly small gaps (50—100 m 2). Although in large gaps (up to 2009 m 2 in the present study) these species usually increased in total number of stems and basal area, they declined in importance relative to species which rarely survived in small gaps but grew rapidly in large gaps. The disturbance regimes in the forests studied favored tolerant species but allowed opportunists to persist at low densities.