Foliar morphology and chemistry of upland oaks, red maple, and sassafras seedlings in response to single and repeated prescribed fires

摘要

Managers increasingly use prescribed fire in oak forests to decrease fire-sensitive species, increase understory light, and improve oak (Quercus spp.) regeneration. To better understand woody seedling response to burning, single and repeated (3x) prescribed fires were implemented over 6 years (2002-2007) in eastern Kentucky, and leaf traits of red (Erythrobalanus spp.) and white oaks (Leucobalanus spp.) were compared with competitors red maple (Acer rubrum L.) and sassafras (Sassafras albidum (Nutt.) Nees). Burned seedlings had higher total leaf area (TLA) because of two to three times higher TLA of sassafras. Leaf mass per area (LMA) and leaf N content per area (N(area)) increased postfire but were independent of seedling identity. Canopy openness during 2006, which was lower on unburned sites (4%-8%) compared with those burned 1x (4%-16%) and 3x (7%-33%), was positively correlated with sassafras TLA, oak and sassafras N(area), and LMA of all seedling groups the subsequent year. In 2007, TLA, LMA, and N(area) were positively correlated with basal diameter of all groups but most significantly for sassafras and red maple. These findings indicate that low-intensity, early growing season prescribed fire can alter seedling leaf characteristics, but not in a manner that enhances oak seedling leaf traits relative to their competitors red maple and sassafras.