Prescribed Fire Alters Structure and Composition of a Mid-Atlantic Oak Forest up to Eight Years After Burning

Background Prescribed fire in Eastern deciduous forests has been understudied relative to other regions in the United States. In Pennsylvania, USA, prescribed fire use has increased more than five-fold since 2009, yet forest response has not been extensively studied. Due to variations in forest composition and the feedback between vegetation and fire, Pennsylvania deciduous forests may burn and respond differently than forests across the eastern US. We measured changes in forest structure and composition up to eight years after prescribed fire in a hardwood forest of the Ridge and Valley region of the Appalachian Mountains in central Pennsylvania. Results Within five years post fire, tree seedling density increased more than 72% while sapling density decreased by 90%, midstory density decreased by 46%, and overstory response varied. Following one burn in the mixed-oak unit, overstory tree density decreased by 12%. In the aspen–oak unit, where pre-fire harvesting and two burns occurred, overstory tree density increased by 25%. Not all tree species responded similarly and post-fire shifts in species relative abundance occurred in sapling and seedling size classes. Abundance of red maple and cherry species decreased, whereas abundance of sassafras, quaking aspen, black oak, and hickory species increased. Conclusions Forest composition plays a key role in the vegetation–fire relationship and localized studies are necessary to measure forest response to prescribed fire. Compositional shifts in tree species were most pronounced in the aspen–oak unit where pre-fire overstory thinning and two prescribed fires were applied and significant structural changes occurred in all stands after just one burn. Increases in fire-tolerant tree species combined with reductions in fire-intolerant species highlight the role of prescribed fire in meeting management objectives such as altering forest structure and composition to improve game habitat in mid-Atlantic hardwood forests

Prescribed fire: Understanding liability, laws and risk

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Characterization of Masticated Fuelbeds and Fuel Treatment Effectiveness in Southeastern US Pine Ecosystems.

Mechanical fuels treatments are being widely used in fire prone ecosystems where fuel loading poses a hazard, yet little research examining fuel dynamics, fire behavior, and ecological effects exists, especially in the southeastern US. In order to broaden our understanding of these treatments, effects of mechanical mastication ( mowing ) were examined in a common pine ecosystem of the southeastern US Coastal Plain, where the post-mastication fuel environment is unique among ecosystems where mastication is being employed. Foliar litter dominates surface fuels after understory mastication in palmetto/gallberry pine flatwoods, however rapid recovery of shrubs quickly regains control over fire behavior. Treatments were effective at reducing flame heights during post-treatment prescribed burning in these sites, however compact surface fuels were observed to cause long-duration heating during laboratory burning. Overstory tree mortality observed following summer burning in mowed treatments may have resulted from combustion of the compact surface fuels beneath the shrub layer. Although temperature and humidity at the shrub level were minimally impacted, drier surface fuels existed in masticated sites where shrub cover was reduced, potentially exacerbating combustibility of the surface fuel layer. Treatments had little impact on understory vegetation communities or soil nutrients, however, observed reduction in saw palmetto may alter future groundcover, as slight increases in grass cover were observed. The fast recovery of understory vegetation and generally low impact to ecosystem attributes suggest resiliency of these pine flatwoods following mechanical treatments. However, their effectiveness at reducing fire hazard is likely short-lived. Treatment regimes that utilize prescribed burning to reduce post-mastication fuels will require special attention to treatment timing in order to ensure surface litter consumption, while minimizing potential impacts to the overstory

Immediate and short-term response of understory fuels following mechanical mastication in a pine flatwoods site of Florida, USA

a b s t r a c t Mechanical fuel hazard reduction treatments are widely implemented in fire-prone ecosystems, but research evaluating their effects on fuel dynamics has focused only on woody-dominated post-treatment fuels. In the southeastern US, one of the most fire-prone regions of the world, mechanical fuels reduction is being increasingly used, yet the resulting fuelbeds have yet to be fully characterized for their fire risk. In order to broaden our understanding of the longevity and effectiveness of these treatments, mechanical mastication (''mowing'') was examined in a common pine ecosystem of the southeastern US Coastal Plain, where the post-mastication fuel environment was dominated by non-woody fuels. Fuel dynamics differed between recently burned mature stands, mature stands that had not burned for several years, and younger pine plantations. Foliar litter dominated (46-69%) the 17.1-23.1 Mg ha À1 of post-mastication surface fuels across these ecosystems, where pre-treatment understories were dominated by palmetto and gallberry shrubs. Although surface fuels compacted over time, the shrub layer recovered quickly, contributing to the result that stand-alone mechanical treatments did not reduce overall fuel loads. Increases in surface fuels followed by rapid shrub recovery may indicate short-term treatment efficacy, with narrow windows of opportunity for post-treatment fuel reduction burns. The fuelbed characteristics and fuel dynamics observed in these treated sites broaden our understanding of mechanical fuels reduction treatments in general, and provide the critical data for fuel model development

Appendix B. Species codes used in Figs. 2, 3, and 4.

Species codes used in Figs. 2, 3, and 4