Mortality, Damage, and Growth in an Oak Woodland Following Prescribed Fire and Commercial Thinning in the Ozark Highlands

by

Carter O. Kinkead, John M. Kabrick, and John M. Kabrick

(COK), Graduate Research Assistant, School of Natural Resources, University of Missouri-Columbia (JMK), Research Forester, USDA Forest Service, North Central Research Station (MCS), Research Associate, Department of Forestry, University of Missouri-Columbia,To contact, email carterkinkead@mail.missouri.edu

Abstract – Maintaining mixed hardwood and oak-pine woodlands may require periods of both frequent, and infrequent prescribed fire, and/or some combination of thinning to achieve desired conditions. The results of our study illustrate a fundamental challenge that managers face when targeting partial stocking levels of open woodlands; that is finding a balanced disturbance regime capable of re-opening canopy structure without causing severe damage to residual trees. Our objectives were to measure three important effects of fire and thinning that should be considered when managing oak woodlands; 1) mortality, 2) damage, and 3) growth of residual trees. Two prescribed fires (BURN) caused only a marginal 1.4% decrease in radial growth of white oaks, compared to a 1.9% decrease in CONTROL. Commercial removals (THIN) resulted in an 84% growth increase, while the combination of these treatments (THIN+BURN) amounted to only a 35% increase in growth rate of retention trees. Cumulative mortality, scar damage, and radial growth of overstory trees > 25 cm DBH were generally unaffected by two prescribed fires, except where thinning operations preceded fires. Red oaks tended to have greater mortality and scarring rates than white oaks, hickories, and shortleaf pine, especially where commercial thinning took place. These findings should help managers evaluate tradeoffs between commercial thinning and prescribed fire when concerned about mortality, damage, and growth of residual woodland trees in the Ozark Highlands.