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FireStem2D--a two-dimensional heat transfer model for simulating tree stem injury in fires.

Chatziefstratiou EK, Bohrer G, Bova AS, Subramanian R, Frasson RP, Scherzer A, Butler BW, Dickinson MB - PLoS ONE (2013)

Bottom Line: It builds on an earlier one-dimensional model (FireStem) and provides improved capabilities for predicting fire-induced mortality and injury before a fire occurs by resolving stem moisture loss, temperatures through the stem, degree of bark charring, and necrotic depth around the stem.We present the results of numerical parameterization and model evaluation experiments for FireStem2D that simulate laboratory stem-heating experiments of 52 tree sections from 25 trees.The model allows for improved understanding and prediction of the effects of wildland fire on injury and mortality of trees of different species and sizes.

View Article: PubMed Central - PubMed

Affiliation: Department of Civil and Environmental Engineering and Geodetic Science, The Ohio State University, Columbus, Ohio, United States of America. chatziefstratiou.1@osu.edu

ABSTRACT
FireStem2D, a software tool for predicting tree stem heating and injury in forest fires, is a physically-based, two-dimensional model of stem thermodynamics that results from heating at the bark surface. It builds on an earlier one-dimensional model (FireStem) and provides improved capabilities for predicting fire-induced mortality and injury before a fire occurs by resolving stem moisture loss, temperatures through the stem, degree of bark charring, and necrotic depth around the stem. We present the results of numerical parameterization and model evaluation experiments for FireStem2D that simulate laboratory stem-heating experiments of 52 tree sections from 25 trees. We also conducted a set of virtual sensitivity analysis experiments to test the effects of unevenness of heating around the stem and with aboveground height using data from two studies: a low-intensity surface fire and a more intense crown fire. The model allows for improved understanding and prediction of the effects of wildland fire on injury and mortality of trees of different species and sizes.

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Forcing pattern and results for Case 1.A. Temperature distribution in the stem at the peak of heating process. B. Schematic illustration of heat forcing that was applied only to the front (upper right quadrant) and lee (lower left quadrant) sides as a plot of heat flux (HF) multiplier vs. the circumferential wedge number. The first wedge is located between 0 and 1.4 degrees from the top (“north”) of the stem and wedge numbers are increased in the clockwise direction. At each wedge, the HF multiplier is applied to the circumferential mean heat-flux forcing. C. Remaining uninjured stem after heating. D. Necrotic depth of each wedge of the stem.
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pone-0070110-g008: Forcing pattern and results for Case 1.A. Temperature distribution in the stem at the peak of heating process. B. Schematic illustration of heat forcing that was applied only to the front (upper right quadrant) and lee (lower left quadrant) sides as a plot of heat flux (HF) multiplier vs. the circumferential wedge number. The first wedge is located between 0 and 1.4 degrees from the top (“north”) of the stem and wedge numbers are increased in the clockwise direction. At each wedge, the HF multiplier is applied to the circumferential mean heat-flux forcing. C. Remaining uninjured stem after heating. D. Necrotic depth of each wedge of the stem.

Mentions: The experiment examines impacts of heat distribution around the tree stem to necrotic depth and its relationship with stem diameter. In our experiment, heat forcing was applied around a virtual P. strobus stem (same properties as previously) in five different ways described in Fig. 8 and Fig. 9. The results show that cases 2, 3, and 5, the cases which heat the stem circumferentially with different intensity distributions, have greater effects than cases 1 and 4, which heat only half of the tree’s circumference, at windward and leeward sides. Case 3 (3/8 of total heat at windward and leeward sides, and 1/8 at each of the other sides) has the greatest effects on the tree stem as it leaves only 79% of the tree’s cross-sectional area unaffected by necrosis. However, the results in that case are only slightly different than cases 2 and 5 which leave 80% and 81% unaffected by necrosis, respectively. In this experiment we did not distinguish between sapwood and the total cross-section area. However, the model results can be used to provide specific predictions for the mortality of different critical tissues within the tree. Empirical knowledge of the depth of sapwood relative to the total DBH exists in many species (e.g., [40]) and could be used to predict necrosis of specifically the sapwood. Table 2 also indicates that the greater the diameter of the tree, the larger percentage of stem cross-sectional area survives and the smaller the possibility for tree mortality.


FireStem2D--a two-dimensional heat transfer model for simulating tree stem injury in fires.

Chatziefstratiou EK, Bohrer G, Bova AS, Subramanian R, Frasson RP, Scherzer A, Butler BW, Dickinson MB - PLoS ONE (2013)

Forcing pattern and results for Case 1.A. Temperature distribution in the stem at the peak of heating process. B. Schematic illustration of heat forcing that was applied only to the front (upper right quadrant) and lee (lower left quadrant) sides as a plot of heat flux (HF) multiplier vs. the circumferential wedge number. The first wedge is located between 0 and 1.4 degrees from the top (“north”) of the stem and wedge numbers are increased in the clockwise direction. At each wedge, the HF multiplier is applied to the circumferential mean heat-flux forcing. C. Remaining uninjured stem after heating. D. Necrotic depth of each wedge of the stem.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3716762&req=5

pone-0070110-g008: Forcing pattern and results for Case 1.A. Temperature distribution in the stem at the peak of heating process. B. Schematic illustration of heat forcing that was applied only to the front (upper right quadrant) and lee (lower left quadrant) sides as a plot of heat flux (HF) multiplier vs. the circumferential wedge number. The first wedge is located between 0 and 1.4 degrees from the top (“north”) of the stem and wedge numbers are increased in the clockwise direction. At each wedge, the HF multiplier is applied to the circumferential mean heat-flux forcing. C. Remaining uninjured stem after heating. D. Necrotic depth of each wedge of the stem.
Mentions: The experiment examines impacts of heat distribution around the tree stem to necrotic depth and its relationship with stem diameter. In our experiment, heat forcing was applied around a virtual P. strobus stem (same properties as previously) in five different ways described in Fig. 8 and Fig. 9. The results show that cases 2, 3, and 5, the cases which heat the stem circumferentially with different intensity distributions, have greater effects than cases 1 and 4, which heat only half of the tree’s circumference, at windward and leeward sides. Case 3 (3/8 of total heat at windward and leeward sides, and 1/8 at each of the other sides) has the greatest effects on the tree stem as it leaves only 79% of the tree’s cross-sectional area unaffected by necrosis. However, the results in that case are only slightly different than cases 2 and 5 which leave 80% and 81% unaffected by necrosis, respectively. In this experiment we did not distinguish between sapwood and the total cross-section area. However, the model results can be used to provide specific predictions for the mortality of different critical tissues within the tree. Empirical knowledge of the depth of sapwood relative to the total DBH exists in many species (e.g., [40]) and could be used to predict necrosis of specifically the sapwood. Table 2 also indicates that the greater the diameter of the tree, the larger percentage of stem cross-sectional area survives and the smaller the possibility for tree mortality.

Bottom Line: It builds on an earlier one-dimensional model (FireStem) and provides improved capabilities for predicting fire-induced mortality and injury before a fire occurs by resolving stem moisture loss, temperatures through the stem, degree of bark charring, and necrotic depth around the stem.We present the results of numerical parameterization and model evaluation experiments for FireStem2D that simulate laboratory stem-heating experiments of 52 tree sections from 25 trees.The model allows for improved understanding and prediction of the effects of wildland fire on injury and mortality of trees of different species and sizes.

View Article: PubMed Central - PubMed

Affiliation: Department of Civil and Environmental Engineering and Geodetic Science, The Ohio State University, Columbus, Ohio, United States of America. chatziefstratiou.1@osu.edu

ABSTRACT
FireStem2D, a software tool for predicting tree stem heating and injury in forest fires, is a physically-based, two-dimensional model of stem thermodynamics that results from heating at the bark surface. It builds on an earlier one-dimensional model (FireStem) and provides improved capabilities for predicting fire-induced mortality and injury before a fire occurs by resolving stem moisture loss, temperatures through the stem, degree of bark charring, and necrotic depth around the stem. We present the results of numerical parameterization and model evaluation experiments for FireStem2D that simulate laboratory stem-heating experiments of 52 tree sections from 25 trees. We also conducted a set of virtual sensitivity analysis experiments to test the effects of unevenness of heating around the stem and with aboveground height using data from two studies: a low-intensity surface fire and a more intense crown fire. The model allows for improved understanding and prediction of the effects of wildland fire on injury and mortality of trees of different species and sizes.

Show MeSH
Related in: MedlinePlus