Research Database
Displaying 61 - 80 of 92
The impact of aging on laboratory fire behaviour in masticated shrub fuelbeds of California and Oregon, USA
Year: 2016
Mastication of shrubs and small trees to reduce fire hazard has become a widespread management practice, yet many aspects of the fire behaviour of these unique woody fuelbeds remain poorly understood. To examine the effects of fuelbed aging on fire behaviour, we conducted laboratory burns with masticated Arctostaphylos spp. and Ceanothus spp. woody debris that ranged from 2 to 16 years since treatment. Masticated fuels that were 10 years or older burned with 18 to 29% shorter flame heights and 19% lower fireline intensities compared with the younger fuelbeds across three different fuel loads…
Publication Type: Journal Article
Predicting large wildfires across western North America by modeling seasonal variation in soil water balance
Year: 2016
A lengthening of the fire season, coupled with higher temperatures, increases the probability of fires throughout much of western North America. Although regional variation in the frequency of fires is well established, attempts to predict the occurrence of fire at a spatial resolution <10 km2 have generally been unsuccessful. We hypothesized that predictions of fires might be improved if depletion of soil water reserves were coupled more directly to maximum leaf area index (LAImax) and stomatal behavior. In an earlier publication, we used LAImax and a process-based forest growth model to…
Publication Type: Journal Article
Synthesis of Knowledge of Extreme Fire Behavior: Volume II for Fire Behavior Specialists, Researchers, and Meteorologists
Year: 2016
The National Wildfire Coordinating Group’s definition of extreme fire behavior indicates a level of fire behavior characteristics that ordinarily precludes methods of direct controlaction. One or more of the following is usually involved: high rate of spread, prolific crowning/ spotting, presence of fire whirls, and strong convection column. Predictability is difficultas such fires often influence their environment to some degree and behave erratically, sometimes dangerously. Alternate terms include “blow up” and “fire storm.” Fire managersexamining fires over the last 100 years have come to…
Publication Type: Report
Places where wildfire potential and social vulnerability coincide in the coterminous United States
Year: 2016
The hazards-of-place model posits that vulnerability to environmental hazards depends on both biophysical and social factors. Biophysical factors determine where wildfire potential is elevated, whereas social factors determine where and how people are affected by wildfire. We evaluated place vulnerability to wildfire hazards in the coterminous US. We developed a social vulnerability index using principal component analysis and evaluated it against existing measures of wildfire potential and wildland–urban interface designations. We created maps showing the coincidence of social vulnerability…
Publication Type: Journal Article
Forest fuels and potential fire behaviour 12 years after variable-retention harvest in lodgepole pine
Year: 2016
Variable-retention harvesting in lodgepole pine offers an alternative to conventional, even-aged management. This harvesting technique promotes structural complexity and age-class diversity in residual stands and promotes resilience to disturbance. We examined fuel loads and potential fire behaviour 12 years after two modes of variable-retention harvesting (dispersed and aggregated retention patterns) crossed by post-harvest prescribed fire (burned or unburned) in central Montana. Results characterise 12-year post-treatment fuel loads. We found greater fuel load reduction in treated than…
Publication Type: Journal Article
Fire and non-native grass invasion interact to suppress tree regeneration in temperate deciduous forests
Year: 2015
While many ecosystems depend on fire to maintain biodiversity, non-native plant invasions can enhance fire intensity, suppressing native species and generating a fire–invasion feedback. These dynamics have been observed in arid and semi-arid ecosystems, but fire–invasion interactions in temperate deciduous forests, where prescribed fires are often used as management tools to enhance native diversity, have rarely been investigated. Here we evaluated the effects of a widespread invasive grass on fire behaviour in eastern deciduous forests in the USA and the potential effects of fire and…
Publication Type: Journal Article
Experimental analysis of fire spread across a two-dimensional ridge under wind conditions
Year: 2015
Results from a laboratory-scale investigation of a fire spreading on the windward face of a triangular-section hill of variable shape with wind perpendicular to the ridgeline are reported. They confirm previous observations that the fire enlarges its lateral spread after reaching the ridgeline, entering the leeward face with a much wider front. Reference fire spread velocities were measured and analysed, putting in evidence the importance of the dynamic effect due to flow velocity and its associated horizontal-axis separation vortex strength without dependence on hill geometry. Similar…
Publication Type: Journal Article
Evaluating crown fire rate of spread predictions from physics-based models
Year: 2015
Modeling the behavior of crown fires is challenging due to the complex set of coupled processes that drive the characteristics of a spreading wildfire and the large range of spatial and temporal scales over which these processes occur. Detailed physics-based modeling approaches such as FIRETEC and the Wildland Urban Interface Fire Dynamics Simulator (WFDS) simulate fire behavior using computational fluid dynamics based methods to numerically solve the three-dimensional, time dependent, model equations that govern, to some approximation, the component physical processes and their interactions…
Publication Type: Journal Article
Put the wet stuff on the hot stuff': The legacy and drivers of conflict surrounding wildfire suppression
Year: 2015
Existing research demonstrates that wildfire events can lead to conflict among local residents and outside professionals involved in wildfire management or suppression. What has been missing in thewildfire literature is a more explicit understanding of the social dynamics that influence such conflict in rural or agricultural communities and their long-term legacy for future wildfire management. Authorsconducted interviews with local residents of a southeastern Washington community in 2012 to better understand conflict surrounding management of the 2006 Columbia Complex Fire. We utilize…
Publication Type: Journal Article
A Wildfire-relevant climatology of the convective environment of the United States
Year: 2015
Convective instability can influence the behaviour of large wildfires. Because wildfires modify the temperature and moisture of air in their plumes, instability calculations using ambient conditions may not accurately represent convective potential for some fire plumes. This study used the North American Regional Reanalysis to develop a climatology of the convective environment specifically tied to large fire events. The climatology is based on the period 1979–2009 and includes ambient convective available potential energy (CAPE) as well as values when surface air is warmed by 0.5, 1.0 or 2.0…
Publication Type: Journal Article
Categorizing the social context of the wildland urban interface: Adaptive capacity for wildfire and community "archetypes"
Year: 2015
Understanding the local context that shapes collective response to wildfire risk continues to be a challenge for scientists and policymakers. This study utilizes and expands on a conceptual approach for understanding adaptive capacity to wildfire in a comparison of 18 past case studies. The intent is to determine whether comparison of local social context and community characteristics across cases can identify community "archetypes" that approach wildfire planning and mitigation in consistently different ways. Identification of community archetypes serves as a potential strategy for…
Publication Type: Journal Article
Long-term dead wood changes in a Sierra Nevada mixed conifer forest: habitat and fire hazard implications
Year: 2015
Dead trees play an important role in forests, with snags and coarse woody debris (CWD) used by many bird and mammal species for nesting, resting, or foraging. However, too much dead wood can also contribute to extreme fire behavior. This tension between dead wood as habitat and dead wood as fuel has raised questions about appropriate quantities in fire-dependent forested ecosystems. Three plots installed in mixed conifer forest of the central Sierra Nevada in 1929 illustrate how amounts and sizes of dead wood have changed through time as a result of logging and fire exclusion. Diameter of…
Publication Type: Journal Article
Winter grazing can reduce wildfire size, intensity and behaviour in a shrub-grassland
Year: 2015
An increase in mega-fires and wildfires is a global issue that is expected to become worse with climate change. Fuel treatments are often recommended to moderate behaviour and decrease severity of wildfires; however, the extensive nature of rangelands limits the use of many treatments. Dormant-season grazing has been suggested as a rangeland fuel treatment, but its effects on fire characteristics are generally unknown. We investigated the influence of dormant-season (winter) grazing by cattle (Bos taurus) on fuel characteristics, fire behaviour and area burned in Wyoming big sagebrush (…
Publication Type: Journal Article
Simulated western spruce budworm defoliation reduces torching and crowning potential: a sensitivity analysis using a physics-based fire model
Year: 2014
The widespread, native defoliator western spruce budworm (Choristoneura occidentalis Freeman) reduces canopy fuels, which might affect the potential for surface fires to torch (ignite the crowns of individual trees) or crown (spread between tree crowns). However, the effects of defoliation on fire behaviour are poorly understood. We used a physics-based fire model to examine the effects of defoliation and three aspects of how the phenomenon is represented in the model (the spatial distribution of defoliation within tree crowns, potential branchwood drying and model resolution). Our…
Publication Type: Journal Article
Fire behavior in masticated fuels: A review
Year: 2014
Mastication is an increasingly common fuels treatment that redistributes “ladder” fuels to the forest floor to reduce vertical fuel continuity, crown fire potential, and fireline intensity, but fuel models do not exist for predicting fire behavior in these fuel types. Recent fires burning in masticated fuels have behaved in unexpected and contradictory ways, likely because the shredded, compact fuel created when trees and shrubs are masticated contains irregularly shaped pieces in mixtures quite different from other woody fuels. We review fuels characteristics and fire behavior in masticated…
Publication Type: Journal Article
Beyond reducing fire hazard: fuel treatment impacts on overstory tree survival
Year: 2014
Fuel treatment implementation in dry forest types throughout the western UnitedStates is likely to increase in pace and scale in response to increasing incidence of large wildfires.While it is clear that properly implemented fuel treatments are effective at reducing hazardousfire potential, there are ancillary ecological effects that can impact forest resilience eitherpositively or negatively depending on the specific elements examined, as well as treatment type,timing, and intensity. In this study, we use overstory tree growth responses, measured sevenyears after the most common fuel…
Publication Type: Journal Article
Living in a tinderbox: wildfire risk perceptions and mitigating behaviors
Year: 2013
The loss of homes to wildfires is an important issue in the USA and other countries. Yet many homeowners living in fire-prone areas do not undertake mitigating actions, such as clearing vegetation, to decrease the risk of losing their home. To better understand the complexity of wildfire risk-mitigation decisions and the role of perceived risk, we conducted a survey of homeowners in a fire-prone area of the front range of the Rocky Mountains in Colorado. We examine the relationship between perceived wildfire risk ratings and risk-mitigating behaviours in two ways. First, we model wildfire…
Publication Type: Journal Article
ArcFuels10 System Overview
Year: 2013
Fire behavior modeling and geospatial analyses can provide tremendous insight for land managers as they grapple with the complex problems frequently encountered in wildfire risk assessments and fire and fuels management planning. Fuel management often is a particularly complicated process in which the benefits and potential impacts of fuel treatments need to be demonstrated in the context of land management goals and public expectations. The fuel treatment planning process is complicated by the lack of data assimilation among fire behavior models and weak linkages to geographic information…
Publication Type: Report