Biophysical processes of tree mortality in surface fires

The mechanisms of tree mortality in surface fires are poorly understood. This thesis uses a process approach to address three fundamental processes governing post-fire tree mortality. First, a lumped capacitance heat transfer model is used to predict branch, bud, and foliage necroses in the convective plume above a low intensity linefire. The model predicts that branches, buds, and foliage will have different necrosis heights and highlights the necessity of including heat transfer processes in estimates of post-fire mortality. Second, forced convection correlations are presented for Picea glauca Moench (Voss) and Pinus contorta Dougl. Ex. Loud. branches and buds across a velocity range typical of linefire plumes. These correlations describe the increased convective resistance of foliage and are used to calculate convection heat transfer coefficients for the crown scorch model. Third, allometrically-derived sapwood area budgets for Populus tremuloides Michx., P. glauca, and P. contorta are used to link vascular cambium and vegetative bud necroses to tree mortality. Sapwood area budgets provide a simple, general framework for predicting tree mortality in surface fires which is based on the fundamental processes driving tree architecture.