Ecological - Second Order
Current methods for predicting fire-induced plant mortality in shrubs and trees are largely empirical. These methods do not exhibit a wide range of applicability and are not readily linked to duff burning, soil heating, and surface fire behavior models. A detailed model predicting the temperature distribution through a tree stem as a function of time for a time varying heat pulse has been developed (see Stem Mortality in Surface Fires. Part III, Linking Stem Heating with Tissue Response for Planning Prescribed Burns by J. Jones and B.W. Webb). Evaluation of model accuracy has required the development of new techniques for quantifying the heat flux at the bark surface and change in temperatures within plant stems. The techniques must work for a range of heating regimes, stem diameters, and tree species. Here, we describe the experimental methodology used for this effort. Data were collected in field and laboratory studies, the methodology used for each varied. Representative cambial temperatures and surface heat fluxes from four species are presented for a range of stem diameters. Typical surface heating fluxes measured in the field studies ranged from 15 to 80 kW-m 2, magnitude and duration depended on fuel type and loading. Fluxes measured in laboratory studies ranged from 15 to 40 kW-m-2. It is anticipated that the methods developed in this study will be used to obtain data for additional species.