Fire Behavior

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Repeated fire altered succession and increased fire behavior in basin big sagebrush–native perennial grasslands

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The structure and composition of sagebrush‐dominated ecosystems have been altered by changes in fire regimes, land use, invasive species, and climate change. This often decreases resilience to disturbance and degrades critical habitat for species of conservation concern. Basin big sagebrush (Artemisia tridentata ssp. tridentata) ecosystems, in particular, are greatly reduced in distribution as land has been converted to agriculture and other land uses. The fire regime, relative proportions of shrub and grassland patches, and the effects of repeated burns in this ecosystem are poorly understood. We quantified postfire patterns of vegetation accumulation and modeled potential fire behavior on sites that were burned and first measured in the late 1980s at John Day Fossil Beds National Monument, Oregon, USA. The area partially reburned 11 yr after the initial fire, allowing a comparison of one vs. two fires. Repeated burns shifted composition from shrub‐dominated to prolonged native herbaceous dominance. Fifteen years following one fire, the native‐dominated herbaceous component was 44% and live shrubs were 39% of total aboveground biomass. Aboveground biomass of twice‐burned sites (2xB; burned 26 and 15 yr prior) was 71% herbaceous and 12% shrub. Twenty‐six years after fire, total aboveground biomass was 113–209% of preburn levels, suggesting a fire‐return interval of 15–25 yr. Frequency and density of Pseudoroegneria spicata and Festuca idahoensis were not modified by fire history, but Poa secunda was reduced by repeated fire, occurring in 84% of plots burned 26 yr prior, 72% of plots burned 15 yr prior, and 49% in 2xB plots. Nonnative annual Bromus tectorum occurred at a frequency of 74%, but at low density with no differences due to fire history. Altered vegetation structure modified fire behavior, with modeled rates of fire spread in 2xB sites double that of once‐burned sites. This suggests that these systems likely were historically composed of a mosaic of shrub and grassland. However, contemporary increases in fire frequency will likely create positive feedbacks of more intense fire behavior and prolonged periods of early‐successional vegetation in basin big sagebrush communities.

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Listening to the flow: Discoveries from wildland fire acoustics

Webinar recording.

Sound is a fundamental part of our experience when interacting with the world around us. So fundamental in fact, that we often forget to question what it is we are hearing. Our long relationship with all aspects of fire, including the sounds of fire, are deeply intuitive and yet elusive. What is creating the crackling sound we hear when vegetation burns? What is it really telling us about the exchange between vegetation and fire? What is making all that “noise” near a fire that causes us to raise our voices as we work or turn to observe with a fresh sense of alert concern? What sounds are involved that lead to a safe or unsettling feeling around wildland fire? In this webinar, I will take a deep dive into the crackling sound of fire; what is this sound really telling us, where is it coming from, and what else is going on besides what we hear?

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Weather, risk, and resource orders on large fires in the western US

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Study results suggest that weather is a primary driver of resource orders over the course of extended attack efforts on large fires. Incident Management Teams (IMTs) synthesize information about weather, fuels, and order resources based on expected fire growth rather than simply reacting to observed fire growth. Analysis shows that incident management teams are generally forward-looking and respond to expected rather than recently observed weather-driven fire behavior. These results may have important implications for forecasting resource needs and costs in a changing climate

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Role of previous fires in the management and expenditures of subsequent large wildfires

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Using a sample of 722 large fires from the western United States, we observe whether a fire interacted with a previous fire, the percent area of fires burned by previous fires, and the percent perimeter overlap with previous fires. Fires that interact with previous fires are likely to be larger and have lower total expenditures on average. Conditional on a fire encountering a previous fire, a greater extent of interaction with previous fires is associated with reduced fire size but higher expenditures, although the expenditure effect is small and imprecisely estimated. Subsequent analysis suggests that fires that interact with previous fires may be systematically different from other fires along several dimensions. We do not find evidence that interactions with previous fires reduce suppression expenditures for subsequent fires. Results suggest that previous fires may allow suppression opportunities that otherwise might not exist, possibly reducing fire size but increasing total expenditures.

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An introduction to the new US National Fire Danger Rating System

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In this webinar, Matt Jolly (Research Ecologist, USDA Forest Service Rocky Mountain Research Station) presents the structure and function of the current version of the US National Fire Danger Rating, NFDRS2016. He shows how this system can be used to assess seasonal variations in fuel moisture and fire potential and how it can be used to quantify fire season severity anywhere in the country. Jolly demonstrates the use of FireFamily+ Version 5.0 to explore local fire weather conditions and suggests ways to use both tabular and graphical displays to communicate fire danger conditions to a variety of audiences such as firefighters, IMT members, fire management officers, line officers and the public. Finally, he introduces new spatial fire danger assessment tools and discuss the future of NFDRS.

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FlamMap 6.0 Fire Modeling System

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This webinar provides an introduction and overview of the FlamMap modeling system and its capabilities. FlamMap is a fire analysis desktop application that describes potential fire behavior (spread rate, flame length, fireline intensity, etc.), fire growth and spread and conditional burn probabilities under constant environmental conditions (weather and fuel moisture). Dead fuel moisture and conditioning of dead fuels in each pixel is based on slope, shading, elevation, aspect, and weather. With the inclusion of FARSITE it can now compute wildfire growth and behavior for longer time periods under heterogeneous conditions of terrain, fuels, fuel moistures and weather.)

With the release of FlamMap 6.0 information from completed fire behavior runs (BASIC, STFB, NTFB) from the Wildland Fire Decision Support System (WFDSS) and the Interagency Fuels Treatment Decision Support System (IFTDSS) can be imported directly into FlamMap6 to setup runs. Additionally, a landscape editing tool has been added, the ability to project geospatial data layers, and a full set of tutorials within the Help System to facilitate learning to operate FlamMap.

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Models inform strategic implementation of management in extreme fire weather

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Our model-informed decision framework illustrated that forest management (thinning and continued prescribed fire) was most effective and critical under extreme fire weather conditions. Using a model to inform on where high-severity fires were most likely to occur allowed for the strategic placement of management prescriptions, which reduced the amount of area requiring mechanical thinning and were just as effective as less strategic approaches in reducing wildfire severity.

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Predictive services comparison tools; Predicting fire behavior in AK; Smoke tools

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The Advanced Fire Environment Learning Unit (AFELU) hosts three speakers to talk about Predictive Services comparison tools, predicting fire behavior in Alaska, and smoke tools. The target audience is anyone interested in fire behavior, fire weather, or fire prediction.

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Fire behavior and smoke modelling: Needs for next-generation forecasting

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This review paper presents simulations and experiments of hypothetical prescribed burns with a suite of selected fire behavior and smoke models and identifies major issues for model improvement and the most critical observational needs. The results are used to understand the new and improved capability required for the next-generation SRF systems and to support the design of the Fire and Smoke Model Evaluation Experiment (FASMEE) and other field campaigns. The next-generation SRF systems should have more coupling of fire, smoke and atmospheric processes. The development of the coupling capability requires comprehensive and spatially and temporally integrated measurements across the various disciplines to characterize flame and energy structure (e.g. individual cells, vertical heat profile and the height of well-mixing flaming gases), smoke structure (vertical distributions and multiple subplumes), ambient air processes (smoke eddy, entrainment and radiative effects of smoke aerosols) and fire emissions (for different fuel types and combustion conditions from flaming to residual smouldering), as well as night-time processes (smoke drainage and super-fog formation).

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A review of US wildland firefighter entrapments: Trends, important environmental factors and research needs

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Examination of the historical literature indicated that entrapment potential peaks when fire behavior rapidly deviates from an assumed trajectory, becomes extreme and compromises the use of escape routes, safety zones or both. Additionally, despite the numerous safety guidelines that have been developed as a result of analyzing past entrapments, we found issues with the way factual information from these incidents is reported, recorded and stored that make quantitative investigations difficult. To address this, a fire entrapment database was assembled that revealed when details about the location and time of entrapments are included in analyses, it becomes possible to ascertain trends in space and time and assess the relative influence of various environmental variables on the likelihood of an entrapment. Several research needs were also identified, which highlight the necessity for improvements in both fundamental knowledge and the tools used to disseminate that knowledge.

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