Process models of post-fire tree growth and mortality

Fire effects on tree growth and mortality result from an interaction of heat injuries to the roots, stem, and crown, but the mechanisms by which these injuries occur and interact are not completely understood. In this talk, I will discuss the current understanding of the physical and physiological mechanisms linking fire behavior to post-fire growth and mortality. First, I will derive and evaluate a process-based mortality model that considers two well-established injuries (meristem necroses in vascular cambium and vegetative buds) and how these can be linked to whole-tree mortality using a sapwood area budget. Second, I will present experimental data showing that heat reduces xylem conductivity via two mechanisms (enhanced air seed cavitation and conduit wall deformation), suggesting that sapwood area reduction is another injury important for post-fire growth and mortality. Third, I will outline a new process-based approach for linking fire behavior to meristem necroses, leaf necrosis, and sapwood area reduction, and how these injuries can be linked to post-fire growth and mortality using a dynamic mass balance approach.