Title: Time to ignition is influenced by both moisture content and soluble carbohydrates in live Douglas fir and Lodgepole pine needles
Author: Jolly, Matt; McAllister, Sara; Finney, Mark; Hadlow, Ann
Source: In: Viegas, D. X., ed. Proceedings of the VI International Conference on Forest Fire Research; 15-18 November 2010; Coimbra, Portugal. Coimbra, Portugal: University of Coimbra. 8 p.
Description: Living plants are often the primary fuels burning in wildland fire but little is known about the factors that govern their ignition behavior. Moisture content has long been hypothesized to determine the characteristics of fires spreading in live fuels but moisture content alone fails to explain observed differences in the ignition of various species at different times of the year. Furthermore, little concern has been given to balance between the moisture content and chemical composition of live fuels and how this balance of might affect the net energy required to produce the combustible mixture of gases that is necessary for flaming combustion. Here we examine the time to ignition of two species of live fuels, Douglas Fir (Pseudotsuga menzeseii) and Lodgepole Pine (Pinus contorta). Live fuels are collected throughout the season and their time to ignition quantified. Additionally, we assess the moisture content and carbohydrate composition of each sample. We found that time to ignition was significantly correlated with moisture content but that moisture content alone only explains about 46% of the variability in time to ignition for both species. However, when moisture content is combined with a simple metric of available carbohydrates, 85% of the variability in ignition timing was explained using the same model for both species. These results suggest that while moisture content plays an important role in determining the time to ignition of live plants, additional information about the distribution of carbon-based compounds in the foliage is equally as important. This metric may serve as a simple way to assess the flammability of foliage and to determine the characteristics that make some plants more easily ignited than others.
Keywords: live fuel, moisture content, carbohydrates, combustion, time to ignition
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Jolly, W. Matt; McAllister, Sara; Finney, Mark; Hadlow, Ann. 2010. Time to ignition is influenced by both moisture content and soluble carbohydrates in live Douglas fir and Lodgepole pine needles. In: Viegas, D. X., ed. Proceedings of the VI International Conference on Forest Fire Research; 15-18 November 2010; Coimbra, Portugal. Coimbra, Portugal: University of Coimbra. 8 p.
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