Canadian Forest Service Publications
Assessing the probability of sustained flaming in masticated fuel beds. 2015. Schiks, T.J.; Wotton, B.M. Canadian Journal of Forest Research 45:68-77.
Available from: Great Lakes Forestry Centre
Catalog ID: 35875
CFS Availability: PDF (request by e-mail)
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Mechanical mastication is increasingly used as a fuel management treatment to reduce fire risk at the wildland–urban interface, although ignition and fire behaviour in these novel fuel beds are poorly understood. We investigated the influence of observed fuel moisture content, wind speed, and firebrand size on the probability of sustained flaming of masticated fuel beds under both laboratory and field settings. Logistic regression techniques were applied to assess the probability of sustained flaming in both datasets. Models for the field were also developed using estimated moisture from three sets of weather-based models: (i) the hourly Fine Fuel Moisture Code (FFMC) from the Canadian Forest Fire Weather Index System, (ii) the National Fire Danger Rating System (NFDRS) moisture estimates for 1 h and 10 h fuels, and (iii) a masticated surface fuel moisture model (MAST). In both laboratory and field testing, the likelihood of a successful ignition increased with decreasing moisture content and increasing wind speed; the effect of firebrand size was only apparent in laboratory testing. The FFMC, NFDRS, and MAST predictions had somewhat reduced discriminative power relative to direct moisture in predicting the probability of sustained flaming based on our field observations. Our results speak to the disparity between the fire behaviour modeling that occurs in the laboratory and the fire behavior modeling that occurs in the field, as the methodology permitted comparison of predictions from sustained flaming models that were developed for one experimental setting and applied to the other.
Plain Language Summary
We wanted to improve our understanding of ignition and fire behaviour in masticated fuel beds. These are areas where trees and understory vegetation have been shredded to create a highly compacted surface fuel bed that disrupts the vertical continuity of forest fuels and reduces fire risk, particularly at the wildland–urban interface. We investigated the influence of moisture content, wind speed, and firebrand size on the probability of sustained flaming under both laboratory and field settings. We found that the likelihood of a successful ignition increased with drier fuels and higher wind speed in both settings. Larger firebrands increased the probability of sustained flaming but the effect was only apparent in laboratory testing. Our results showed the disparity between fire behaviour in the laboratory and the field and the importance of a complete assessment of fire behaviour to produce accurate models.
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