Bark charcoal reflectance may have the potential to estimate the heat delivered to tree boles by wildland fires

Abstract

Currently, our ability to link wildland fire behaviour to fire effects is through the lens of fire severity assessments, because there are no ground-based post-fire metrics that are able to quantitively capture aspects of heat transfer to plants. This presents a particular challenge when considering tree mortality linked to cambial damage, which can occur in both low-intensity surface fires through to high-intensity crown fires. Recent research suggests that measuring the amount of light reflected from charcoals produced by wildland fires will provide information about the energy flux that created the char. We created an experimental forest fire in which we had instrumented individual trees to record the energy delivered to the bark close to the base of the trees. We then assessed the bark charcoal reflectance of the same trees. We found that bark charcoal reflectance showed a strong positive correlation (r2>0.86, P=0.0031) with increasing duration of heating and the total energy delivered to the bark. We suggest that this may provide useful quantitative data that can be included in models or post-fire surveys to estimate tree mortality due to cambial kill.