Research Database
Displaying 41 - 60 of 189
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
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
Moderating effects of past wildfire on reburn severity depend on climate and initial severity in Western US forests
Year: 2024
Rising global fire activity is increasing the prevalence of repeated short-interval burning (reburning) in forests worldwide. In forests that historically experienced frequent-fire regimes, high-severity fire exacerbates the severity of subsequent fires by increasing prevalence of shrubs and/or by creating drier understory conditions. Low- to moderate-severity fire, in contrast, can moderate future fire behavior by reducing fuel loads. The extent to which previous fires moderate future fire severity will powerfully affect fire-prone forest ecosystem trajectories over the next century. Further…
Publication Type: Journal Article
Ladder fuels rather than canopy volumes consistently predict wildfire severity even in extreme topographic-weather conditions
Year: 2024
Drivers of forest wildfire severity include fuels, topography and weather. However, because only fuels can be actively managed, quantifying their effects on severity has become an urgent research priority. Here we employed GEDI spaceborne lidar to consistently assess how pre-fire forest fuel structure affected wildfire severity across 42 California wildfires between 2019–2021. Using a spatial-hierarchical modeling framework, we found a positive concave-down relationship between GEDI-derived fuel structure and wildfire severity, marked by increasing severity with greater fuel loads until a…
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
Tamm review: A meta-analysis of thinning, prescribed fire, and wildfire effects on subsequent wildfire severity in conifer dominated forests of the Western US
Year: 2024
Increased understanding of how mechanical thinning, prescribed burning, and wildfire affect subsequent wildfire severity is urgently needed as people and forests face a growing wildfire crisis. In response, we reviewed scientific literature for the US West and completed a meta-analysis that answered three questions: (1) How much do treatments reduce wildfire severity within treated areas? (2) How do the effects vary with treatment type, treatment age, and forest type? (3) How does fire weather moderate the effects of treatments? We found overwhelming evidence that mechanical thinning with…
Publication Type: Journal Article
Stream chemical response is mediated by hydrologic connectivity and fire severity in a Pacific Northwest forest
Year: 2024
Large-scale wildfires are becoming increasingly common in the wet forests of the Pacific Northwest (USA), with predicted increases in fire prevalence under future climate scenarios. Wildfires can alter streamflow response to precipitation and mobilize water quality constituents, which pose a risk to aquatic ecosystems and downstream drinking water treatment. Research often focuses on the impacts of high-severity wildfires, with stream biogeochemical responses to low- and mixed-severity fires often understudied, particularly during seasonal shifts in hydrologic connectivity between hillslopes…
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
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
Higher burn severity stimulates postfire vegetation and carbon recovery in California
Year: 2023
As the climate continues to warm, the severity of wildfires is increasing. However, the potential impact of higher burn severity on ecosystem resilience and regional carbon balance is still not clear. There are ongoing debates regarding whether increased burn severity stimulates or delays postfire vegetation and carbon recovery. In this study, we utilized remote sensing data to analyze burn severity and vegetation observations, as well as model simulations to assess wildfire carbon emissions and ecosystem carbon fluxes. Our focus was on examining the dynamics of vegetation and carbon flux…
Publication Type: Journal Article
Fire severity infuences large wood and stream ecosystem responses in western Oregon watersheds
Year: 2023
Background. Wildfre is a landscape disturbance important for stream ecosystems and the recruitment of large wood (LW; LW describes wood in streams) into streams, with post-fre management also playing a role. We used a stratifed random sample of 4th-order watersheds that represent a range of pre-fre stand age and fre severity from unburned to entirely burned watersheds to 1) determine whether watershed stand age (pre-fre) or fre severity afected riparianoverstory survival, riparian coarse wood (CW; CW describes wood in riparian areas), LW, or in-stream physical, chemical, and biological…
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
The outsized role of California’s largest wildfires in changing forest burn patterns and coarsening ecosystem scale
Year: 2023
Highlights • We evaluated trends for 1,809 fires that burned 1985–2020 across California forests. • Top 1% of fires by size burned 47% of total area burned across the study period. • Top 1% (18 fires) produced 58% of high and 42% of low-moderate severity area. • Top 1% created novel landscape patterns of large burn severity patches. • These large fires create new opportunities for managing forest resilience. Although recent large wildfires in California forests are well publicized in media and scientific literature, their cumulative effects on forest structure and implications for forest…
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
Effects of nurse shrubs and biochar on planted conifer seedling survival and growth in a high-severity burn patch in New Mexico, USA
Year: 2023
The synergistic effects of widespread high-severity wildfire and anthropogenic climate change are driving large-scale vegetation conversion. In the southwestern United States, areas that were once dominated by conifer forests are now shrub- or grasslands after high-severity wildfire, an ecosystem conversion that could be permanent without human intervention. Yet, the reforestation of these landscapes is rarely successful, with a mean planted seedling survival of just 25 %. Given these low rates, we carried out a planting experiment to quantify the impacts of biochar as a soil amendment and…
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
Low-intensity fires mitigate the risk of high-intensity wildfires in California’s forests
Year: 2023
The increasing frequency of severe wildfires demands a shift in landscape management to mitigate their consequences. The role of managed, low-intensity fire as a driver of beneficial fuel treatment in fire-adapted ecosystems has drawn interest in both scientific and policy venues. Using a synthetic control approach to analyze 20 years of satellite-based fire activity data across 124,186 square kilometers of forests in California, we provide evidence that low-intensity fires substantially reduce the risk of future high-intensity fires. In conifer forests, the risk of high-intensity fire is…
Publication Type: Journal Article
Spatial interactions among short-interval fires reshape forest landscapes
Year: 2023
Aim Ecological disturbances are increasing as climate warms, and how multiple disturbances interact spatially to drive landscape change is poorly understood. We quantified burn severity across fire regimes in reburned forest landscapes to ask how spatial patterns of high-severity fire differ between sequential overlapping fires and how landscape heterogeneity is shaped by cumulative disturbance patterns. We also characterized the amount and configuration of an emerging phenomenon: areas burned as high-severity fire twice in successive fires. Location Northwest USA. Time period 1984–2020.…
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
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