The effects of intermediate-scale wind disturbance on forest composition, structure, and succession with implications for management
Forest disturbances are discrete events in space and time that disrupt the biophysical environment and impart lasting legacies on forest composition, structure, and stand development. Intermediate-scale disturbances may promote stand heterogeneity, including uneven-aged structure, and their effects can range in size and distribution from small, patchy gaps to the removal of large portions of overstory vegetation. These events are often classified along gradients of intensity, which in this study were defined using post-tornado aerial photographs and visual assessments in the field. The specific objectives of this study, which took place two growing seasons after an EF1 tornado, were to quantify and compare canopy structure, understory light regimes, woody species composition, and species diversity along a gradient of canopy disturbance and to analyze the influence of intermediate-scale disturbance on the successional trajectory of an upland hardwood forest. We found no significant differences in tree layer Shannon diversity among the control (no storm damage), moderately, or severely disturbed plots. We found significant differences (P < 0.01) in percent of intercepted PAR between the control and severe classes and between moderate and severe classes. This disturbance acted primarily as a release mechanism for advanced regeneration and stems in the midstory. Our results can be used to refine silvicultural prescriptions that attempt to minimize the disparity between managed and unmanaged stands and to promote intra-stand heterogeneity.