Research Database
Displaying 21 - 40 of 74
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
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
Biogeographic patterns of daily wildfire spread and extremes across North America
Year: 2024
Introduction: Climate change is predicted to increase the frequency of extreme single-day fire spread events, with major ecological and social implications. In contrast with well-documented spatio-temporal patterns of wildfire ignitions and perimeters, daily progression remains poorly understood across continental spatial scales, particularly for extreme single-day events (“blow ups”). Here, we characterize daily wildfire spread across North America, including occurrence of extreme single-day events, duration and seasonality of fire and extremes, and ecoregional climatic…
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
Fire refugia are robust across Western US forested ecoregions, 1986–2021
Year: 2023
In the Western US, area burned and fire size have increased due to the influences of climate change, long-term fire suppression leading to higher fuel loads, and increased ignitions. However, evidence is less conclusive about increases in fire severity within these growing wildfire extents. Fires burn unevenly across landscapes, leaving islands of unburned or less impacted areas, known as fire refugia. Fire refugia may enhance post-fire ecosystem function and biodiversity by providing refuge to species and functioning as seed sources after fires. In this study, we evaluated whether the…
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
Refuge-yeah or refuge-nah? Predicting locations of forest resistance and recruitment in a fiery world
Year: 2023
Climate warming, land use change, and altered fire regimes are driving ecological transformations that can have critical effects on Earth's biota. Fire refugia—locations that are burned less frequently or severely than their surroundings—may act as sites of relative stability during this period of rapid change by being resistant to fire and supporting post-fire recovery in adjacent areas. Because of their value to forest ecosystem persistence, there is an urgent need to anticipate where refugia are most likely to be found and where they align with environmental conditions that support post-…
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
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
Interactions Between Fire Refugia and Climate-Environment Conditions Determine Mesic Subalpine Forest Recovery After Large and Severe Wildfires
Year: 2022
Infrequent stand-replacing wildfires are characteristic of mesic and/or cool conifer forests in western North America, where forest recovery within high-severity burn patch interiors can be slow, yet successful over long temporal periods (decades to centuries). Increasing fire frequency and high-severity burn patch size, under a warming climate, however, may challenge post-fire forest recovery, promoting landscape-level shifts in forest structure, composition, and distribution of non-forest patches. Crucial to a delay and/or impediment to this shift, fire refugia (i.e., remnant seed sources)…
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
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
Where and why do conifer forests persist in refugia through multiple fire events?
Year: 2021
Changing wildfire regimes are causing rapid shifts in forests worldwide. In particular, forested landscapes that burn repeatedly in relatively quick succession may be at risk of conversion when pre-fire vegetation cannot recover between fires. Fire refugia (areas that burn less frequently or severely than the surrounding landscape) support post-fire ecosystem recovery and the persistence of vulnerable species in fire-prone landscapes. Observed and projected fire-induced forest losses highlight the need to understand where and why forests persist in refugia through multiple fires. This…
Publication Type: Journal Article
Disjunct and decoupled? The persistence of a fire-sensitive conifer soecies in a historically frequent-fire landscape
Year: 2020
Local and regional species extirpations may become more common as changing climate and disturbance regimesaccelerate species’ in situ range contractions. Identifying locations that function as both climate and disturbancerefugia is critical for biodiversity conservation. Here, we investigate the persistence of a disjunct, fire-sensitiveconifer population, yellow-cedar (Callitropsis nootkatensis), in the historically frequent-fire landscape of the BlueMountains in eastern Oregon, USA. We used tree rings to reconstruct multi-century fire histories, which werethen used to compare historical mean…
Publication Type: Journal Article
Fire behaviour and smoke modelling: model improvement and measurement needs for next-generation smoke research and forecasting systems
Year: 2019
There is an urgent need for next-generation smoke research and forecasting (SRF) systems to meet the challenges of the growing air quality, health and safety concerns associated with wildland fire emissions. This review paper presents simulations and experiments of hypothetical prescribed burns with a suite of selected fire behaviour 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…
Publication Type: Journal Article
Contributions of fire refugia to resilient ponderosa pine and dry mixed-conifer forest landscapes
Year: 2019
Altered fire regimes can drive major and enduring compositional shifts or losses of forest ecosystems. In western North America, ponderosa pine and dry mixed‐conifer forest types appear increasingly vulnerable to uncharacteristically extensive, high‐severity wildfire. However, unburned or only lightly impacted forest stands that persist within burn mosaics—termed fire refugia—may serve as tree seed sources and promote landscape recovery. We sampled tree regeneration along gradients of fire refugia proximity and density at 686 sites within the perimeters of 12 large wildfires that occurred…
Publication Type: Journal Article