Using Infrared Imagery to Assess Fire Behaviour in a Mulched Fuel Bed in Black Spruce Forests

Brett Moore,Joshua M Johnston,Steven Hvenegaard,Dan K Thompson,Dave Schroeder

doi:10.3390/fire3030037

Brett Moore, Joshua M Johnston + Show 3 more

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https://doi.org/10.3390/fire3030037

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Abstract

An experimental fire was conducted in one-year-old mulched (masticated) boreal fuels, where all aboveground biomass was mulched with no stems removed or left standing. Typical mulching practices remove remnant biomass; leaving biomass in situ reduces overall management input. While fuel quantities were not explicitly reduced, availability of fuels to fire was reduced. Infrared imagery was obtained to quantify rate of spread and intensity to a 1 m resolution. In-stand totalizing heat flux sensors allowed for the observation of energy release near the surface. When compared with the pre-treatment fuel-type M-2 (mixedwood, 50% conifer), rates of spread were reduced 87% from an expected 8 m min−1 to observed values 1.2 m min−1. Intensity was also reduced from 5000 kWm−1 to 650kWm−1 on average. Intermittent gusts caused surges of fire intensity upwards of 5000 kW m−1 as captured by the infrared imagery. With reference to a logging slash fuel type, observed spread rates declined by 87% and intensity 98%. Independent observations of energy release rates from the radiometers showed similar declines. As mulching is a prevalent fuel management technique in Alberta, Canada, future studies will contribute to the development of a fire behaviour prediction model.

Highlights

Fuel management to reduce fire intensity, in particular mulching [1], has become increasingly prevalent as communities seek for ways to prepare for and defend from wildfires
The fire was started from a point ignition at 15:00 local time
The results indicate that future test burns should focus on conditions with higher wind speeds and drier conditions to determine if there is a weather or Fire Weather Index System (FWI) threshold at which point mulch fires cannot be safely actioned by fire crews

Summary

Introduction

Fuel management to reduce fire intensity, in particular mulching ( known as mastication) [1], has become increasingly prevalent as communities seek for ways to prepare for and defend from wildfires. A number of fuel management techniques are being used on the landscape that are similar to the mulching performed in this study, such as stand thinning and clearcutting. During this mulching treatment, remnant fuels remain in situ as opposed to a typical pile and burn strategy to remove the fuels. Remnant fuels remain in situ as opposed to a typical pile and burn strategy to remove the fuels This is a key difference from standard fuel management techniques as the total available fuel is not reduced but converted to mulch and displaced

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