Research Database
Displaying 1 - 20 of 23
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
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
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
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
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
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
High-severity burned area and proportion exceed historic conditions in Sierra Nevada, California, and adjacent ranges
Year: 2023
Although fire is a fundamental ecological process in western North American forests, climate warming and accumulating forest fuels due to fire suppression have led to wildfires that burn at high severity across larger fractions of their footprint than were historically typical. These trends have spiked upwards in recent years and are particularly pronounced in the Sierra Nevada–Southern Cascades ecoregion of California, USA, and neighboring states. We assessed annual area burned (AAB) and percentage of area burned at high and low-to-moderate severity for seven major forest types in this…
Publication Type: Journal Article
Postglacial vegetation and fire history with a high-resolution analysis of tephra impacts, High Cascade Range, Oregon, USA
Year: 2023
The postglacial history of vegetation, wildfire, and climate in the Cascade Range (Oregon) is only partly understood. This study uses high-resolution macroscopic charcoal and pollen analysis from a 13-m, 14,500 years sediment record from Gold Lake, located in a montane forest, to reconstruct forest vegetation and fire history. The occurrence of three tephra layers, including a 78-cm airfall Mazama tephra, as well as highly laminated segments, allows one to study tephra impacts on vegetation at a fine temporal resolution. From the Late Glacial through the Younger Dryas, pollen spectra vary…
Publication Type: Journal Article
Changes in wildfire occurrence and risk to homes from 1990 through 2019 in the Southern Rocky Mountains, USA
Year: 2023
Wildfires and housing development have increased since the 1990s, presenting unique challenges for wildfire management. However, it is unclear how the relative influences of housing growth and changing wildfire occurrence have altered risk to homes, or the potential for wildfire to threaten homes. We used a random forests model to predict burn probability in relation to weather variables at 1-km resolution and monthly intervals from 1990 through 2019 in the Southern Rocky Mountains ecoregion. We quantified risk by combining the predicted burn probabilities with decadal housing density. We…
Publication Type: Journal Article
Response of forest productivity to changes in growth and fire regime due to climate change
Year: 2023
Climate change is having complex impacts on the boreal forest, modulating both tree growth limiting factors and fire regime. However, these aspects are usually projected independently when estimating climate change effect on the boreal forest. Using a combination of 3 different methods, our goal is to assess the combined impact of changes in growth and fire regime due to climate change on the timber supply at the transitions from closed to open boreal coniferous forests in Québec, Canada. In order to identify the areas that are likely to be the most sensitive to climate change, we projected…
Publication Type: Journal Article
Consistent spatial scaling of high-severity wildfire can inform expected future patterns of burn severity
Year: 2023
Increasing wildfire activity in forests worldwide has driven urgency in understanding current and future fire regimes. Spatial patterns of area burned at high severity strongly shape forest resilience and constitute a key dimension of fire regimes, yet remain difficult to predict. To characterize the range of burn severity patterns expected within contemporary fire regimes, we quantified scaling relationships relating fire size to patterns of burn severity. Using 1615 fires occurring across the Northwest United States between 1985 and 2020, we evaluated scaling relationships within fire…
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
Abrupt, climate-induced increase in wildfires in British Columbia since the mid-2000s
Year: 2023
In the province of British Columbia, Canada, four of the most severe wildfire seasons of the last century occurred in the past 7 years: 2017, 2018, 2021, and 2023. To investigate trends in wildfire activity and fire-conducive climate, we conducted an analysis of mapped wildfire perimeters and annual climate data for the period of 1919–2021. Results show that after a century-long decline, fire activity increased from 2005 onwards, coinciding with a sharp reversal in the wetting trend of the 20th century. Even as precipitation levels remain high, moisture deficits have increased due to rapid…
Publication Type: Journal Article
Does large area burned mean a bad fire year? Comparing contemporary wildfire years to historical fire regimes informs the restoration task in fire-dependent forests
Year: 2023
Wildfires and fire seasons are commonly rated largely on the simple metric of area burned (more hectares: bad). A seemingly paradoxical narrative frames large fire seasons as a symptom of a forest health problem (too much fire), while simultaneously stating that fire-dependent forests lack sufficient fire to maintain system resilience (too little fire). One key to resolving this paradox is placing contemporary fire years in the context of historical fire regimes, considering not only total fire area but also burn severity distributions. Historical regimes can also inform forest restoration…
Publication Type: Journal Article
Widespread exposure to altered fire regimes under 2 °C warming is projected to transform conifer forests of the Western United States
Year: 2023
Changes in wildfire frequency and severity are altering conifer forests and pose threats to biodiversity and natural climate solutions. Where and when feedbacks between vegetation and fire could mediate forest transformation are unresolved. Here, for the western United States, we used climate analogs to measure exposure to fire-regime change; quantified the direction and spatial distribution of changes in burn severity; and intersected exposure with fire-resistance trait data. We measured exposure as multivariate dissimilarities between contemporary distributions of fire frequency, burn…
Publication Type: Journal Article
The eco-evolutionary role of fire in shaping terrestrial ecosystems
Year: 2023
1. Fire is an inherently evolutionary process, even though much more emphasis has been given to ecological responses of plants and their associated communities to fire. 2. Here, we synthesize contributions to a Special Feature entitled ‘Fire as a dynamic ecological and evolutionary force’ and place them in a broader context of fire research. Topics covered in this Special Feature include a perspective on the im-pacts of novel fire regimes on differential forest mortality, discussions on new ap-proaches to investigate vegetation-fire feedbacks and resulting plant syndromes,…
Publication Type: Journal Article
Evidence for multi-decadal fuel buildup in a large California wildfire from smoke radiocarbon measurements
Year: 2023
In recent decades, there has been a significant increase in annual area burned in California's Sierra Nevada mountains. This rise in fire activity has prompted the need to understand how historical forest management practices affect fuel composition and emissions. Here we examined the total carbon (TC) concentration and radiocarbon abundance (Δ14C) of particulate matter (PM) emitted by the KNP Complex Fire, which occurred during California's 2021 wildfire season and affected several groves of giant sequoia trees in the southern Sierra Nevada. During a 26 h sampling period, we measured…
Publication Type: Journal Article
How Does Fire Suppression Alter the Wildfire Regime? A Systematic Review
Year: 2023
Fire suppression has become a fundamental approach for shaping contemporary wildfire regimes. However, a growing body of research suggests that aggressive fire suppression can increase high-intensity wildfires, creating the wildfire paradox. Whether the strategy always triggers the paradox remains a topic of ongoing debate. The role of fire suppression in altering wildfire regimes in diverse socio-ecological systems and associated research designs demands a deeper understanding. To reconcile these controversies and synthesize the existing knowledge, a systematic review has been conducted to…
Publication Type: Journal Article
Climate influences on future fire severity: a synthesis of climate-fire interactions and impacts on fire regimes, high-severity fire, and forests in the western United States
Year: 2023
Background
Increases in fire activity and changes in fire regimes have been documented in recent decades across the western United States. Climate change is expected to continue to exacerbate impacts to forested ecosystems by increasing the frequency, size, and severity of wildfires across the western United States (US). Warming temperatures and shifting precipitation patterns are altering western landscapes and making them more susceptible to high-severity fire. Increases in large patches of high-severity fire can result in significant impacts to landscape processes and ecosystem function…
Publication Type: Journal Article