Research Database
Displaying 21 - 40 of 81
Drivers and Impacts of the Record-Breaking 2023 Wildfire Season in Canada
Year: 2024
The 2023 wildfire season in Canada was unprecedented in its scale and intensity, spanning from mid-April to late October and across much of the forested regions of Canada. Here, we summarize the main causes and impacts of this exceptional season. The record-breaking total area burned (~15 Mha)can be attributed to several environmental factors that converged early in the season: early snowmelt, multi annual drought conditions in western Canada, and the rapid transition to drought in eastern Canada. Anthropogenic climate change enabled sustained extreme fire weather conditions, as the meanMay–…
Publication Type: Journal Article
Drought before fire increases tree mortality after fire
Year: 2024
Fire and drought are expected to increase in frequency and severity in temperate forests due to climate change. To evaluate whether drought increases the likelihood of post-fire tree mortality, we used a large database of tree survival and mortality from 32 years of wildland fires covering four dominant western North American conifers. We used Bayesian hierarchical modeling to predict the probability of individual tree mortality after fire based on species—Pinus contorta (lodgepole pine), Abies concolor (white fir), Pseudotsuga menziesii (Douglas-fir), and Pinus…
Publication Type: Journal Article
Review of fuel treatment effects on fuels, fire behavior and ecological resilience in sagebrush (Artemisia spp.) ecosystems in the Western U.S.
Year: 2024
BackgroundSagebrush ecosystems are experiencing increases in wildfire extent and severity. Most research on vegetation treatments that reduce fuels and fire risk has been short term (2–3 years) and focused on ecological responses. We review causes of altered fire regimes and summarize literature on the longer-term effects of treatments that modify (1) shrub fuels, (2) pinyon and juniper canopy fuels, and (3) fine herbaceous fuels. We describe treatment effects on fuels, fire behavior, ecological resilience, and resistance to invasive annual grasses.ResultsOur review revealed tradeoffs in…
Publication Type: Journal Article
Hydrometeorology-wildfire relationship analysis based on a wildfire bivariate probabilistic framework in different ecoregions of the continental United States
Year: 2024
Wildfires are a natural part of the ecosystem in the U.S.. It is vital to classify wildfires using a comprehensive approach that simultaneously considers wildfire activity (the number of wildfires) and burned area. On this basis, the influence of hydrometeorological variables on wildfires can be further analyzed. Therefore, this study first classified wildfire types using a wildfire bivariate probability framework. Then, by considering six hydrometeorological variables, the dominant hydrometeorological variables for different wildfire types in 17 ecoregions of the United States were…
Publication Type: Journal Article
Estimating masticated and cone fuel loads using the Photoload method
Year: 2024
BackgroundRecognizing the complexity and varied nature of forest fuelbeds is crucial in understanding fire behavior and effects on the landscape. While current modeling efforts often consider fine and coarse woody debris surface fuel loads, those options do not always provide the most complete description of the fuelbeds. Both masticated fuels and cones can be a significant part of the fuelbed, with the potential to influence fire behavior and effects, but they are not currently captured in planar intersect methods or Photoload fuel sampling methodology. Cones are prevalent in most forested…
Publication Type: Journal Article
Characterizing post-fire delayed tree mortality with remote sensing: sizing up the elephant in the room
Year: 2024
BackgroundDespite recent advances in understanding the drivers of tree-level delayed mortality, we lack a method for mapping delayed mortality at landscape and regional scales. Consequently, the extent, magnitude, and effects of delayed mortality on post-fire landscape patterns of burn severity are unknown. We introduce a remote sensing approach for mapping delayed mortality based on post-fire decline in the normalized burn ratio (NBR). NBR decline is defined as the change in NBR between the first post-fire measurement and the minimum NBR value up to 5 years post-fire for each pixel…
Publication Type: Journal Article
State of Wildfires 2023–2024
Year: 2024
Climate change contributes to the increased frequency and intensity of wildfires globally, with significant impacts on society and the environment. However, our understanding of the global distribution of extreme fires remains skewed, primarily influenced by media coverage and regionalised research efforts. This inaugural State of Wildfires report systematically analyses fire activity worldwide, identifying extreme events from the March 2023–February 2024 fire season. We assess the causes, predictability, and attribution of these events to climate change and land use and forecast future risks…
Publication Type: Journal Article
Fuel constraints, not fire weather conditions, limit fire behavior in reburned boreal forests
Year: 2024
Fire frequency in boreal forests has increased via longer burning seasons, drier conditions, and higher temperatures. However, fires have historically self-regulated via fuel limitations, mediating the effects of changes in climate and fire weather. Early post-fire boreal forests (10–15 years postfire) are often dominated by mixed conifer-broadleaf or broadleaf regeneration, considered less flammable due to the higher foliar moisture of broadleaf trees and shrubs compared to their more intact conifer counterparts. However, the strength of self-regulation in the context of changing fire…
Publication Type: Journal Article
Vertical and Horizontal Crown Fuel Continuity Influences Group-Scale Ignition and Fuel Consumption
Year: 2023
A deeper understanding of the influence of fine-scale fuel patterns on fire behavior is essential to the design of forest treatments that aim to reduce fire hazard, enhance structural complexity, and increase ecosystem function and resilience. Of particular relevance is the impact of horizontal and vertical forest structure on potential tree torching and large-tree mortality. It may be the case that fire behavior in spatially complex stands differs from predictions based on stand-level descriptors of the fuel distribution and structure. In this work, we used a spatially explicit fire behavior…
Publication Type: Journal Article
Recent Douglas-fir Mortality in the Klamath Mountains Ecoregion of Oregon: Evidence for a Decline Spiral
Year: 2023
Recent increases in Douglas-fir (Psuedotsuga menziesii var. menziesii) mortality in the Klamath Mountains ecoregion raise concerns about the long-term resilience of Douglas-fir in the ecoregion and increased potential for uncharacteristic wildfire. We used data from the USDA Forest Service Aerial Detection Survey and ninety-six field plots to explore the relationships between physiographic and climate variables and Douglas-fir mortality. Our results provide strong evidence for a decline spiral in which Douglas-fir growing on hot, dry sites (predisposing factor) are further stressed by drought…
Publication Type: Journal Article
Heading and backing fire behaviours mediate the influence of fuels on wildfire energy
Year: 2023
Background: Pre-fire fuels, topography, and weather influence wildfire behaviour and fire-driven ecosystem carbon loss. However, the pre-fire characteristics that contribute to fire behaviour and effects are often understudied for wildfires because measurements are difficult to obtain. Aims: This study aimed to investigate the relative contribution of pre-fire conditions to fire energy and the role of fire advancement direction in fuel consumption. Methods: Over 15 years, we measured vegetation and fuels in California mixed-conifer forests within days before and after wildfires, with co-…
Publication Type: Journal Article
Consistent, high-accuracy mapping of daily and sub-daily wildfire growth with satellite observations
Year: 2023
Background: Fire research and management applications, such as fire behaviour analysis and emissions modelling, require consistent, highly resolved spatiotemporal information on wildfire growth progression. Aims: We developed a new fire mapping method that uses quality-assured sub-daily active fire/thermal anomaly satellite retrievals (2003–2020 MODIS and 2012–2020 VIIRS data) to develop a high-resolution wildfire growth dataset, including growth areas, perimeters, and cross-referenced fire information from agency reports. Methods: Satellite fire detections were buffered using a historical…
Publication Type: Journal Article
Intermittent fireline behaviour over porous vegetative media in different crossflow conditions
Year: 2023
Background: Reliable wildfire prediction and efficient controlled burns require a comprehensive understanding of physical mechanisms controlling fire spread behaviour. Earlier studies explored the intermittent nature of free-burning fires, but the influence of flame intermittency on fire spread requires further attention. Aims: This research qualitatively explores dynamic fire behaviour and its influence on fire spread. Methods: Fire spread experiments were conducted under varying wind conditions inside a wind tunnel. Various cameras were used for qualitative analysis, verified against…
Publication Type: Journal Article
Quantifying the flammability of living plants at the branch scale: which metrics to use?
Year: 2023
Background
Plant flammability is an important factor in fire behaviour and post-fire ecological responses. There is consensus about the broad attributes (or axes) of flammability but little consistency in their measurement.
Aims
We sought to provide a pathway towards greater consistency in flammability research by identifying a subset of preferred flammability metrics for living plants.
Methods
Flammability was measured at the branch scale using a range of metrics for 140 plant specimens in an apparatus that simulates an approaching fire front.
Key results
We identified a subset…
Publication Type: Journal Article
Prescribed fire after thinning increased resistance of sub-Mediterranean pine forests to drought events and wildfires
Year: 2023
Vegetation structure affects the vulnerability of a forest to drought events and wildfires. Management decisions, such as thinning intensity and type of understory treatment, influence competition for water resources and amount of fuel available. While heavy thinning effectively reduces tree water stress and intensity of a crown fire, the duration of these benefits may be limited by a fast growth response of the understory. Our aim was to study the effect of forest structure on pine forests vulnerability to extreme drought events and on the potential wildfire behaviour after management, with…
Publication Type: Journal Article
Less fuel for the next fire? Short-interval fire delays forest recovery and interacting drivers amplify effects
Year: 2023
As 21st-century climate and disturbance dynamics depart from historic baselines, ecosystem resilience is uncertain. Multiple drivers are changing simultaneously, and interactions among drivers could amplify ecosystem vulnerability to change. Subalpine forests in Greater Yellowstone (Northern Rocky Mountains, USA) were historically resilient to infrequent (100–300 year), severe fire. We sampled paired short-interval (<30-year) and long-interval (>125-year) post-fire plots most recently burned between 1988 and 2018 to address two questions: (1) How do short-interval fire, climate,…
Publication Type: Journal Article
Changes in fire behavior caused by fire exclusion and fuel build-up vary with topography in California montane forests, USA
Year: 2022
Wildfire sizes and proportions burned with high severity effects are increasing in seasonally dry forests, especially in the western USA. A critical need in efforts to restore or maintain these forest ecosystems is to determine where fuel build-up caused by fire exclusion reaches thresholds that compromise resilience to fire. Empirical studies identifying drivers of fire severity patterns in actual wildfires can be confounded by co-variation of vegetation and topography and the stochastic effects of weather and rarely consider long-term changes in fuel caused by fire exclusion. To overcome…
Publication Type: Journal Article
Merging prescribed fires and timber harvests in the Sierra Nevada: Burn season and pruning influences in young mixed conifer stands
Year: 2022
Highlights • Mortality of canopy trees was similar between spring and fall prescribed burns in 13-14 year old stands • Fall burns consumed more surface fuel without substantially high levels of canopy damage • Pre-fire pruning Pinus lambertiana and Calocecrus decurrens trees did not clearly reduce tree damage • Gap-based silviculture and prescribed fire can be merged to meet broad ecological goals Abstract In dry, productive forests where historically infrequent high-severity fires are now common, new silvicultural systems will be needed to better align management activity with the ecosystem'…
Publication Type: Journal Article
Extreme fire spread events and area burned under recent and future climate in the western USA
Year: 2022
Aim: Wildfire activity in recent years is notable not only for an expansion of total area burned but also for large, single-day fire spread events that pose challenges to ecological systems and human communities. Our objectives were to gain new insight into the relationships between extreme single-day fire spread events, annual area burned, and fire season climate and to predict changes under future warming. Location: Fire-prone regions of the western USA. Time period: 2002–2020; a future +2°C scenario. Methods: We used a satellite-derived dataset of daily fire spread events and gridded…
Publication Type: Journal Article
Short- and long-term effects of ponderosa pine fuel treatments intersected by the Egley Fire Complex, Oregon, USA
Year: 2019
Background Fuel treatments are widely used to alter fuels in forested ecosystems to mitigate wildfire behavior and effects. However, few studies have examined long-term ecological effects of interacting fuel treatments (commercial harvests, pre-commercial thinnings, pile and burning, and prescribed fire) and wildfire. Using annually fitted Landsat satellite-derived Normalized Burn Ratio (NBR) curves and paired pre-fire treated and untreated field sites, we tested changes in the differenced NBR (dNBR) and years since treatment as predictors of biophysical attributes one and nine years after…
Publication Type: Journal Article