Recognition of the role of wildland fire in forested ecosystems of the eastern US has increased in recent decades, with greater interest in the use of prescribed fire after several recent high-profile wildfires. To effectively plan wildland fire management, land managers in the eastern US require information on fire’s effects on tree survival. The First Order Fire Effects Model (FOFEM) is an empirical model developed to predict tree mortality following fire using bark thickness (derived from tree diameter) and crown scorch estimates. Bark thickness is a key factor determining tree injury or mortality from fire, especially surface fire. Since bark thickness changes with stem size, FOFEM estimates bark as a species-specific proportion to stem size and assumes bark thickness follows a simple linear allometric relationship across stem sizes. However, the accuracy of these bark thickness estimates has never been independently tested. Using a dataset compiled from experimental prescribed burn studies throughout the eastern US, we compared FOFEM mortality predictions following one fire to empirical results. We then evaluated the accuracy of bark thickness estimates across stem sizes for various tree species by destructive sampling.
Results/Conclusions
There were no relationships between levels of predicted stand-level mortality and measured mortality (p ≥ 0.1704) across a range of modeled fire intensities. Modeled probability of tree mortality varies by species and decreases with tree size based on species-specific, linear equations used to predict bark thickness from tree diameter. We develop new bark thickness equations for common eastern species, accounting for regional differences and non-linear relationships between bark thickness and tree diameter when appropriate. We recommend that these newly developed bark thickness equations be used to calibrate FOFEM’s logistic regression equation for tree mortality to better inform ecological outcomes to surface fires. Results from this work will provide a useful empirical model for fire management planning in eastern forests, and these improved equations will allow for forest managers to more effectively restore ecological functions with prescribed burning through an improved understanding of tree mortality to fire in their forested ecosystems.