Tuesday, 18 November 2003: 9:00 AM
Stem Mortality in Surface Fires. Part III, Linking Stem Heating with Tissue Response for Planning Prescribed BurnsPoster PDF (131.6 kB)
A one-dimensional model for predicting stem heating during wildland fires has been developed. The numerical model includes the dependence of wood/bark thermophysical properties on temperature and moisture. A key aspect of the model is the implementation of an imposed heat flux condition at the boundary of the stem. Such a boundary condition lends itself more readily to coupling with fire behavior simulators. Additionally, the thermal aspects of desiccation, bark swelling, devolatilization, and charring are treated in an approximate fashion for the first time in such a model. With predicted local temperature/time behavior, the simulations can be coupled to the tissue thermal response/mortality model of Dickinson (Stem Mortality in Surface Fires. Part I, Tissue Response to Elevated Temperatures. This coupling provides a tool for predicting depth-of-kill and/or stem mortality. A model evaluation exercise was carried out for four species including two western conifers (Douglas fir and Ponderosa pine) and two central hardwoods (Chestnut oak and Red maple). Model evaluation was carried out in a dual approach: i) comparison of predicted cambial temperature histories with those measured experimentally by Jimenez et al. (Stem Mortality in Surface Fires. Part II, Experimental Measurements of the Thermal Response of Tree Stems to Heating by Fires) for the western softwood species, and ii) comparison of depth-of-kill/stem mortality measurements of Dickinson (Part I) for the central hardwoods. Model predictions compare favorably with both measured temperatures and the stem mortality characterizations.