HR: 0800h
AN: B41B-0120    [Abstracts]
TI: Heat Transfer Processes Linking Fire Behavior and Tree Mortality
AU: * Michaletz, S T
EM: stmichal@ucalgary.ca
AF: Department of Biological Sciences and Kananaskis Field Stations, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4 Canada
AU: Johnson, E A
EM: johnsone@ucalgary.ca
AF: Department of Biological Sciences and Kananaskis Field Stations, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4 Canada
AB: Traditional methods for predicting post-fire tree mortality employ statistical models which neglect the processes linking fire behavior to physiological mortality mechanisms. Here we present a physical process approach which predicts tree mortality by linking fireline intensity with lateral (vascular cambium) and apical (vegetative bud) meristem necrosis. We use a linefire plume model with independently validated conduction and lumped capacitance heat transfer analyses to predict lethal meristem temperatures in tree stems, branches, and buds. These models show that meristem necrosis in large diameter (Bi $\geq$ 0.3) stems/branches is governed by meristem height, bark thickness, and bark water content, while meristem necrosis in small diameter (Bi $<$ 0.3) branches/buds is governed by meristem height, branch/bud size, branch/bud water content, and foliage architecture. To investigate effects of interspecfic variation in these properties, we compare model results for {\it Picea glauca} (Moench) Voss and {\it Pinus contorta} Loudon var. latifolia Engelm. at fireline intensities from 50 to 3000 kWm$^{-1}$. Parameters are obtained from allometric models which relate stem/branch diameter to bark thickness and height, as well as bark and bud water content data collected in the southern Canadian Rocky Mountains. Variation in foliage architecture is quantified using forced convection heat transfer coefficients measured in a laminar flow wind tunnel at Re from 100 to 2000, typical for branches/buds in a linefire plume. Results indicate that in unfoliated stems/branches, {\it P. glauca} meristems are more protected due to thicker bark, whereas in foliated branches/buds, {\it P. contorta} meristems are more protected due to larger bud size and foliage architecture.
UR: http://www.bio.ucalgary.ca/divisions/ecology/johnson.html
DE: 3367 Theoretical modeling
DE: 1851 Plant ecology
DE: 0400 Biogeosciences
DE: 0614 Biological effects
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting