Effects of intermediate-scale wind disturbance on mixed pine-hardwood stands: a comparison of natural and managed disturbance

by

Benjamin Trammell, Justin Hart, Callie Schweitzer, and Dan Dey

University of Alabama

Abstract – All forest ecosystems are subject to natural disturbances that can influence developmental and successional pathways. Intermediate-scale disturbances (ISD) occur along the severity gradient between gaps created by the loss of a single or several canopy trees and disturbances that remove most or all overstory vegetation. Although ISD events disrupt larger areas than gap-scale events and have a shorter return interval than the lifespan of most canopy trees in eastern North America, few studies have quantified their effects on forest ecosystems. For this study, we sampled a mixed pine (Pinus)-hardwood forest impacted by a natural ISD (EF1 tornado). We quantified the compositional and structural characteristics along a gradient of disturbance severity (control, light, moderate) using basal area removed, light levels, and hemispherical photographs. At each 0.04 ha fixed-radius overstory vegetation plot we recorded species, crown class, decay class of all woody stems ≥ 5 cm dbh. Nested 10 m2 regeneration plots were used to quantify regeneration patterns by tallying and identifying all stems <5 cm dbh. We then compared these data to those from a study on a managed site that was thinned to comparable disturbance levels based on basal area removed. Few studies have quantified the effects of ISD and then compared then them to the effects of silvicultural entries in mixed pine-hardwood systems. The results of this study will provide quantitative data on the effects of ISD, and may be used to translate these effects into compositional and structural targets for silvicultural entries in mixed pine-hardwood forests.