Effects of intermediate-scale wind disturbance on composition, structure, and succession in Quercus stands: Implications for natural disturbance-based silviculture
Forest disturbances are discrete events in space and time that disrupt the biophysical environment and impart lasting legacies on forest composition and structure. Disturbances are often classified along a gradient of spatial extent and magnitude that ranges from catastrophic events where most of the overstory is removed to gap-scale events that modify local environmental conditions only. Without question, a paucity of data is available on disturbance events of the intermediate scale (i.e. those events too localized to be classed as catastrophic and too widespread to be considered gap scale). The specific objectives of this study were to quantify and compare canopy structure, understory light regimes, woody species composition, and tree species diversity along a gradient of canopy disturbance caused by an EF1 tornado and to analyze the influence of intermediate-scale disturbance on the successional trajectory of an upland Quercus forest. Statistically significant differences in diversity measures between control (no storm damage), light, or moderate damage class plots were only found in the sapling layer. We documented significant differences (P < 0.01) in percent of intercepted PAR between the control and moderate damage classes and between moderate and light classes. Three growing seasons post-disturbance, the understory light regime had largely returned to pre-disturbance conditions. The disturbance event acted primarily as a release mechanism for advanced reproduction in the understory and for stems in the midstory. Our results provide quantitative information on disturbances of this extent and magnitude and can be used to guide silvicultural systems designed to emulate natural disturbance processes, which is an increasingly popular management approach especially on public lands.