Research Database
Displaying 21 - 40 of 117
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
The Distribution of Tree Biomass Carbon within the Pacific Coastal Temperate Rainforest, a Disproportionally Carbon Dense Forest
Year: 2024
Spatially explicit global estimates of forest carbon storage are typically coarsely scaled. While useful, these estimates do not account for the variability and distribution of carbon at management scales. We asked how climate, topography, and disturbance regimes interact across and within geopolitical boundaries to influence tree biomass carbon, using the perhumid region of the Pacific Coastal Temperate Rainforest, an infrequently disturbed carbon dense landscape, as a test case. We leveraged permanent sample plots in southeast Alaska and coastal British Columbia and used multiple quantile…
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
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
Montane springs provide regeneration refugia after high-severity wildfire
Year: 2024
In the mountainous regions of the Western United States, increasing wildfire activity and climate change are putting forests at risk of regeneration failure and conversion to non-forests. During periods with unfavorable climatic conditions, locations that are suitable for post-fire tree regeneration (regeneration refugia) may be essential for forest recovery. These refugia could provide scattered islands of recovering forest from which broader forest recovery may be facilitated. Spring ecosystems provide cool and wet microsites relative to the surrounding landscape and may act as regeneration…
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
Soil microbiome feedbacks during disturbance-driven forest ecosystem conversion
Year: 2024
Disturbances cause rapid changes to forests, with different disturbance types and severities creating unique ecosystem trajectories that can impact the underlying soil microbiome. Pile burning—the combustion of logging residue on the forest floor—is a common fuel reduction practice that can have impacts on forest soils analogous to those following high-severity wildfire. Further, pile burning following clear-cut harvesting can create persistent openings dominated by nonwoody plants surrounded by dense regenerating conifer forest. A paired 60-year chronosequence of burn scar openings and…
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
Carbon, climate, and natural disturbance: a review of mechanisms, challenges, and tools for understanding forest carbon stability in an uncertain future
Year: 2024
In this review, we discuss current research on forest carbon risk from natural disturbance under climate change for the United States, with emphasis on advancements in analytical mapping and modeling tools that have potential to drive research for managing future long-term stability of forest carbon. As a natural mechanism for carbon storage, forests are a critical component of meeting climate mitigation strategies designed to combat anthropogenic emissions. Forests consist of long-lived organisms (trees) that can store carbon for centuries or more. However, trees have finite lifespans, and…
Publication Type: Journal Article
Branching out: species-specific canopy architecture limits live crown fuel consumption in Intermountain West USA conifers
Year: 2024
Accurate estimates of available live crown fuel loads are critical for understanding potential wildland fire behavior. Existing crown fire behavior models assume that available crown fuels are limited to all tree foliage and half of the fine branches less than 6 mm in diameter (1 h fuel). They also assume that this relationship is independent of the branchwood moisture content. Despite their widespread use, these assumptions have never been tested, and our understanding of the physiochemical properties that govern live crown flammability and consumption remains limited. To test these…
Publication Type: Journal Article
Disentangling drivers of annual grass invasion: Abiotic susceptibility vs. fire-induced conversion to cheatgrass dominance in the sagebrush biome
Year: 2024
Invasive annual grasses are often facilitated by fire, yet they can become ecologically dominant in susceptible locations even in the absence of fire. We used an extensive vegetation plot database to model susceptibility to the invasive annual grass cheatgrass (Bromus tectorum L.) in the sagebrush biome as a function of climate and soil water availability variables. We built random forest models predicting cheatgrass presence or dominance (>15 % relative cover) under unburned (37,219 plots) and burned conditions (6340 plots). We mapped predicted probability of cheatgrass…
Publication Type: Journal Article
Forest structural complexity and ignition pattern influence simulated prescribed fire effects
Year: 2024
Forest structural characteristics, the burning environment, and the choice of ignition pattern each influence prescribed fire behaviors and resulting fire effects; however, few studies examine the influences and interactions of these factors. Understanding how interactions among these drivers can influence prescribed fire behavior and effects is crucial for executing prescribed fires that can safely and effectively meet management objectives. To analyze the interactions between the fuels complex and ignition patterns, we used FIRETEC, a three-dimensional computational fluid dynamics fire…
Publication Type: Journal Article
Landsat assessment of variable spectral recovery linked to post-fire forest structure in dry sub-boreal forests
Year: 2024
Forest disturbances such as wildfires can dramatically alter forest structure and composition, increasing the likelihood of ecosystem changes. Up-to-date and accurate measures of post-disturbance forest recovery in managed forests are critical, particularly for silvicultural planning. Measuring the live and dead vegetation post-fire is challenging because areas impacted by wildfire may be remote, difficult to access, and/or dangerous to survey. The difficulties of post-fire monitoring are compounded by the global increase in the frequency and severity of disturbances, as expansion of…
Publication Type: Journal Article
Generating fuel consumption maps on prescribed fire experiments from airborne laser scanning
Year: 2024
Background. Characterisation of fuel consumption provides critical insights into fire behaviour, effects, and emissions. Stand-replacing prescribed fire experiments in central Utah offered an opportunity to generate consumption estimates in coordination with other research efforts. Aims. We sought to generate fuel consumption maps using pre- and post-fire airborne laser scanning (ALS) and ground measurements and to test the spatial transferability of the ALSderived fuel models. Methods. Using random forest (RF), we empirically modelled fuel load and estimated consumption from pre-…
Publication Type: Journal Article
Road fragment edges enhance wildfire incidence and intensity, while suppressing global burned area
Year: 2024
Landscape fragmentation is statistically correlated with both increases and decreases in wildfire burned area (BA). These different directions-of-impact are not mechanistically understood. Here, road density, a land fragmentation proxy, is implemented in a CMIP6 coupled land-fire model, to represent fragmentation edge effects on fire-relevant environmental variables. Fragmentation caused modelled BA changes of over ±10% in 16% of [0.5°] grid-cells. On average, more fragmentation decreased net BA globally (−1.5%), as estimated empirically. However, in recently-deforested tropical areas,…
Publication Type: Journal Article
High-severity fire drives persistent floristic homogenization in human-altered forests
Year: 2023
Ecological disturbance regimes across the globe are being altered via direct and indirect human influences. Biodiversity loss at multiple scales can be a direct outcome of these shifts. Fire, especially in dry forests, is an ecological disturbance that is experiencing dramatic changes due to climate change, fire suppression, increased human population in fire-prone areas, and alterations to vegetation composition and structure. Dry western conifer forests that historically experienced frequent, low-severity fires are now increasingly burning at high severity. Relatively little work has been…
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
The century-long shadow of fire exclusion: Historical data reveal early and lasting effects of fire regime change on contemporary forest composition
Year: 2023
Historical logging practices and fire exclusion have reduced the proportion of pine in mixed-conifer forests of the western United States. To better understand pine’s decline, we investigate the impact of historical logging on the tree regeneration layer and subsequent stand development over almost a century of fire exclusion. We use a unique dataset derived from contemporary (∼2016) remeasurement of 440 historical quadrats (∼4m2) in the central Sierra Nevada, California, in which overstory trees, tree regeneration, and microsite conditions were measured and mapped both before and after…
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