Fuel dynamics during oak woodland and savanna restoration in the Mid-South USA

Abstract

Thinning and burning can restore imperilled oak woodlands and savannas in the Southern Appalachian and Central Hardwood regions of the USA, but concomitant effects on fuels are less understood. We monitored (2008 to 2016) fuel load response to replicated combinations of thinning (none, 7, and 14m2ha−1 residual basal area) and seasonal fire (none, March, and October) at three sites. All treatments except burn-only increased total fuel loading. Thinning doubled (+16Mgha−1) 1000-h fuels relative to controls, and three fires in 6 years did not eliminate this difference. Increasing thinning intensity did not consistently enhance the combustion of larger fuels. October fires reduced 100- and 10-h fuels more than March fires. Burning alone reduced leaf litter and 1-h twigs by 30%. Burning after thinning doubled this reduction but increased herbaceous fuels 19-fold. Herbaceous fuels increased at a rate that suggests compensation for losses in woody fine fuels with continued burning. Where fuel reduction is a goal, restoration strategies could be more intentionally designed; however, oak woodlands and savannas are inherently more flammable than closed-canopy forests. Management decisions will ultimately involve weighing the risks associated with increased fuel loads against the benefits of restoring open oak communities.