Effects of fuel morphology on ember generation characteristics at the tree scale
Tyler R. Hudson A C , Ryan B. Bray A , David L. Blunck A , Wesley Page B and Bret Butler B
+ Author Affiliations
- Author Affiliations
A School of Mechanical, Industrial, and Manufacturing Engineering, Oregon State University, Corvallis, OR 97331, USA.
B Fire, Fuel, and Smoke Science Program, Rocky Mountain Research Station, USDA Forest Service, Missoula, MT 59808, USA.
C Corresponding author. Email: tyler.robert.hudson@gmail.com
International Journal of Wildland Fire 29(11) 1042-1051 https://doi.org/10.1071/WF19182
Submitted: 1 November 2019 Accepted: 21 July 2020 Published: 19 August 2020
Abstract
This work reports characteristics of embers generated by torching trees and seeks to identify the important physical and biological factors involved. The size of embers, number flux and propensity to ignite spot fires (i.e. number flux of ‘hot’ embers) are reported for several tree species under different combinations of number (one, three or five) and moisture content (11–193%). Douglas-fir (Pseudotsuga menziesii), grand fir (Abies grandis), western juniper (Juniperus occidentalis) and ponderosa pine (Pinus ponderosa) trees were evaluated. Embers were collected on an array of fire-resistant fabric panels and trays filled with water. Douglas-fir trees generated the highest average ember flux per kilogram of mass loss during torching, whereas grand fir trees generated the highest ‘hot’ ember flux per kilogram of mass loss. Western juniper produced the largest fraction of ‘hot’ embers, with ~30% of the embers generated being hot enough to leave char marks. In contrast, only 6% of the embers generated by ponderosa pine were hot enough to leave char marks. Results from this study can be used to help understand the propensity of different species of tree to produce embers and the portion of embers that may be hot enough to start a spot fire.
Additional keywords: fire behaviour, fuel, trees, wildland–urban interface.
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