Abstract
Stand-level fuel reduction treatments in the Canadian boreal zone are used predominantly in community protection settings to alter the natural structure of dominant boreal conifer stands such as black spruce (Picea mariana (Mill.) BSP), jack pine (Pinus banksiana Lamb.) and lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia). The aim of these fuel treatments is to inhibit the development of fast-spreading, high-intensity crown fires that naturally occur in boreal forest ecosystems. We document fuel treatment design standards used in boreal forests in Canada and review data requirements and methodological approaches for investigating fuel treatment effects on fire behaviour. Through a series of illustrative examples and summaries of empirical observations, we explore the implications of data and modelling assumptions used to estimate fire behaviour in fuel-treated areas and identify insights about fuel treatment effectiveness in boreal conifer stands. Fuel treatments in black spruce, jack pine and lodgepole pine stands were generally effective at reducing modelled and observed fire behaviour and inhibiting crown fire development and spread under low to moderate fire weather conditions. Evidence suggests that fuel treatments in these fuel types will be ineffective when rates of spread and wind speeds are very high or extreme. High surface fuel loads combined with the relatively short stature of boreal conifer trees can further undermine fuel treatment efforts. Priority areas for future study include examining alternatives for managing surface fuel loads in treated stands, exploring the viability of alternative horizontal fuel reduction protocols such as clumped fuel configurations, and integrating suppression and containment strategies within the fuel treatment planning and design process.
Highlights
The North American boreal zone traverses the entire Canadian land base (Figure 1, [1]) and is characterized by high-intensity, crown fire ecosystems fueled by conifer species that have coevolved with wildfire [2,3]
C-2, C-3, and C-4 fuel types derived from the relationship between postfire observations of forest floor consumption and the Buildup Index (BUI, [70]), a unitless relative rating of fuel moisture in the organic layer that is calculated from the Duff Moisture Code (DMC) and Drought Code (DC)
Observations of Fuel Treatment Effects—Experimental Fires and Wildfires In Section 3, we demonstrated the process of inputting pre- and post-treatment fuel metrics into various modelling frameworks to explore the effects of fuel treatments on predicted fire behaviour
Summary
The North American boreal zone traverses the entire Canadian land base (Figure 1, [1]) and is characterized by high-intensity, crown fire ecosystems fueled by conifer species that have coevolved with wildfire [2,3]. Latifolia) stands vary by tree species [4] and factors such as stand age [5,6]; at maturity, these stands commonly present in dense, even-aged structures, with a continuous canopy of fuels that can support high-intensity crown fires [2,3]. The propensity of is assisted by the flaky bark fuels that are characteristic of these stands [5]. The propensity of boreal boreal conifer stands to support high-intensity crown fires makes them a hazard and a priority for conifer stands to support high-intensity crowninfires makes to them a hazardareas and alike priority for proactive proactive fuel management when they occur proximity high-value communities [18].
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