Research Database
Displaying 81 - 100 of 182
Evaluating Model Predictions of Fire Induced Tree Mortality Using Wildfire-Affected Forest Inventory Measurements
Year: 2019
Forest land managers rely on predictions of tree mortality generated from fire behavior models to identify stands for post-fire salvage and to design fuel reduction treatments that reduce mortality. A key challenge in improving the accuracy of these predictions is selecting appropriate wind and fuel moisture inputs. Our objective was to evaluate postfire mortality predictions using the Forest Vegetation Simulator Fire and Fuels Extension (FVS-FFE) to determine if using representative fire-weather data would improve prediction accuracy over two default weather scenarios. We used pre- and post-…
Publication Type: Journal Article
A Classification of US Wildland Firefighter Entrapments Based on Coincident Fuels, Weather, and Topography
Year: 2019
Previous attempts to identify the environmental factors associated with firefighter entrapments in the United States have suggested that there are several common denominators. Despite the widespread acceptance of the assumed commonalities, few studies have quantified how often entrapments actually meet these criteria. An analysis of the environmental conditions at the times and locations of 166 firefighter entrapments involving 1202 people and 117 fatalities that occurred between 1981 and 2017 in the conterminous United States revealed some surprising results. Contrary to general assumptions…
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
Examining post-fire vegetation recovery with Landsat time series analysis in three western North American forest types
Year: 2019
Background: Few studies have examined post-fire vegetation recovery in temperate forest ecosystems with Landsat time series analysis. We analyzed time series of Normalized Burn Ratio (NBR) derived from LandTrendr spectral-temporal segmentation fitting to examine post-fire NBR recovery for several wildfires that occurred in three different coniferous forest types in western North America during the years 2000 to 2007. We summarized NBR recovery trends, and investigated the influence of burn severity, post-fire climate, and topography on post-fire vegetation recovery via random forest (RF)…
Publication Type: Journal Article
Defining extreme wildfire events: Difficulties, challenges, and impacts
Year: 2018
Every year worldwide some extraordinary wildfires occur, overwhelming suppression capabilities, causing substantial damages, and often resulting in fatalities. Given their increasing frequency, there is a debate about how to address these wildfires with significant social impacts, but there is no agreement upon terminology to describe them. The concept of extreme wildfire event (EWE) has emerged to bring some coherence on this kind of events. It is increasingly used, often as a synonym of other terms related to wildfires of high intensity and size, but its definition remains elusive. The goal…
Publication Type: Journal Article
Human-related ignitions concurrent with high winds promote large wildfires across the USA
Year: 2018
Large wildfires (>40 ha) account for the majority of burned area across the contiguous United States (US) and appropriate substantial suppression resources. A variety of environmental and social factors influence wildfire growth and whether a fire overcomes initial attack efforts and becomes a large wildfire. However, little is known about how these factors differ between lightning-caused and human-caused wildfires. This study examines differences in temperature, vapour pressure deficit, fuel moisture and wind speed for large and small lightning- and human-caused wildfires during the…
Publication Type: Journal Article
Influence of landscape structure, topography, and forest type on spatial variation in historical fire regimes, Central Oregon, USA
Year: 2018
Context In the interior Northwest, debate over restoring mixed-conifer forests after a century of fire exclusion is hampered by poor understanding of the pattern and causes of spatial variation in historical fire regimes. Objectives To identify the roles of topography, landscape structure, and forest type in driving spatial variation in historical fire regimes in mixed-conifer forests of central Oregon. Methods We used tree rings to reconstruct multicentury fire and forest histories at 105 plots over 10,393 ha. We classified fire regimes into four types and assessed whether they varied with…
Publication Type: Journal Article
Long-Term Effects of Fire on Vegetation Structure and Predicted Fire Behavior in Wyoming Big Sagebrush Ecosystems
Year: 2018
Fire historically occurred across the sagebrush steppe, but little is known about how patterns of post-fire fuel accumulation influence future fire in Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) communities. To quantify change in fuel composition and structure in intact sagebrush ecosystems, we sampled 17 years following prescribed fire in eight approximately 400 ha plots (4 burned, 4 unburned control) at Hart Mountain National Antelope Refuge, OR, USA. Fuels data were used to model potential fire behavior in burn and control plots across four environmental scenarios that…
Publication Type: Journal Article
The nature of the beast: examining climate adaptation options in forests with stand‐replacing fire regimes
Year: 2018
Building resilience to natural disturbances is a key to managing forests for adaptation to climate change. To date, most climate adaptation guidance has focused on recommendations for frequent‐fire forests, leaving few published guidelines for forests that naturally experience infrequent, stand‐replacing wildfires. Because most such forests are inherently resilient to stand‐replacing disturbances, and burn severity mosaics are largely indifferent to manipulations of stand structure (i.e., weather‐driven, rather than fuel‐driven fire regimes), we posit that pre‐fire climate adaptation options…
Publication Type: Journal Article
Evidence for scale‐dependent topographic controls on wildfire spread
Year: 2018
Wildfire ecosystems are thought to be self‐regulated through pattern–process interactions between ignition frequency and location, and patterns of burned and recovering vegetation. Yet, recent increases in the frequency of large wildfires call into question the application of self‐organization theory to landscape resilience. Topography represents a stable bottom‐up template upon which fire interacts as both a physical and an ecological process. However, it is unclear how topographic control changes geographically and across spatial scales. We analyzed fire perimeter and topography data from…
Publication Type: Journal Article
Advancing the Science of Wildland Fire Dynamics Using Process-Based Models
Year: 2018
As scientists and managers seek to understand fire behavior in conditions that extend beyond the limits of our current empirical models and prior experiences, they will need new tools that foster a more mechanistic understanding of the processes driving fire dynamics and effects. Here we suggest that process-based models are powerful research tools that are useful for investigating a large number of emerging questions in wildland fire sciences. These models can play a particularly important role in advancing our understanding, in part, because they allow their users to evaluate the potential…
Publication Type: Journal Article
Expanding Our Understanding of Forest Structural Restoration Needs in the Pacific Northwest
Year: 2018
Ecological departure, or how much landscapes have changed from a natural range of variation (NRV), has become a key metric in forest planning and restoration efforts. In this study we define forest restoration need as the specific change in structural stage abundance necessary to move landscapes into the NRV. While most restoration projects in the forested ecosystems of the Pacific Northwest, USA (Oregon and Washington) have embraced this paradigm, our understanding of what treatments to apply where, when, and at what magnitude is evolving and continues to be refined. We build on a body of…
Publication Type: Journal Article
Fuel Treatments: Are we doing enough?
Year: 2018
Although a natural ecological process, wildfire in unhealthy forests can be uncharacteristically destructive. Fuel treatments—such as thinning, mowing, prescribed fire, or managed wildfire—can help reduce or redistribute the flammable fuels that threaten to carry and intensify fire. Using both field-tested data and computer simulations, Pacific Northwest Research Station scientists are addressing critical questions such as Are we treating enoughof the landscape to restore fire-adapted forests? Are fuel treatments effective at changing fire behavior? Together with land managers, fuel planners…
Publication Type: Report
Land surveys show regional variability of historical fire regimes and dry forest structure of the western United States
Year: 2018
An understanding of how historical fire and structure in dry forests (ponderosa pine, dry mixed conifer) varied across the western United States remains incomplete. Yet, fire strongly affects ecosystem services, and forest restoration programs are underway. We used General Land Office survey reconstructions from the late 1800s across 11 landscapes covering ~1.9 million ha in four states to analyze spatial variation in fire regimes and forest structure. We first synthesized the state of validation of our methods using 20 modern validations, 53 historical cross‐validations, and corroborating…
Publication Type: Journal Article
Embracing Complexity to Advance the Science of Wildland Fire Behavior
Year: 2018
Wildland fire behavior research has largely focused on the steady-state interactions between fuels and heat fluxes. Contemporary research is revealing new questions outside the bounds of this simplified approach. Here, we explore the complex interactions taking place beyond steady-state assumptions through acknowledging the manufactured separation of research disciplines in fire science and the dynamic interactions that unfold when these separations are removed. Through a series of examples spanning at least four research disciplines and three ranges of spatial scale, we illustrate that by…
Publication Type: Journal Article
Regional and local controls on historical fire regimes of dry forests and woodlands in the Rogue River Basin, Oregon, USA
Year: 2018
Fire regimes structure plant communities worldwide with regional and local factors, including anthropogenic fire management, influencing fire frequency and severity. Forests of the Rogue River Basin in Oregon, USA, are both productive and fire-prone due to ample winter precipitation and summer drought; yet management in this region is strongly influenced by forest practices that depend on fire exclusion. Regionally, climate change is increasing fire frequency, elevating the importance of understanding historically frequent-fire regimes. We use cross-dated fire-scars to characterize historical…
Publication Type: Journal Article
Prescribed fire regimes subtly alter ponderosa pine forest plant community structure
Year: 2018
Prescribed fire is an active management tool used to address wildfire hazard and ecological concerns associated with fire exclusion and suppression over the past century. Despite widespread application in the United States, there is considerable inconsistency and lack of information regarding the extent to which specific outcomes are achieved and under what prescribed fire regimes, particularly in regard to ecological goals related to plant community structure. We quantify differences and patterns in plant functional group abundance, species richness and diversity, and other key forest…
Publication Type: Journal Article
Advancing Dendrochronological Studies of Fire in the United States
Year: 2018
Dendroecology is the science that dates tree rings to their exact calendar year of formation to study processes that influence forest ecology (e.g., Speer 2010 [1], Amoroso et al., 2017 [2]). Reconstruction of past fire regimes is a core application of dendroecology, linking fire history to population dynamics and climate effects on tree growth and survivorship. Since the early 20th century when dendrochronologists recognized that tree rings retained fire scars (e.g., Figure 1), and hence a record of past fires, they have conducted studies worldwide to reconstruct [2] the historical range and…
Publication Type: Journal Article
Fire frequency drives decadal changes in soil carbon and nitrogen and ecosystem productivity
Year: 2018
Fire frequency is changing globally and is projected to affect the global carbon cycle and climate. However, uncertainty about how ecosystems respond to decadal changes in fire frequency makes it difficult to predict the effects of altered fire regimes on the carbon cycle; for instance, we do not fully understand the long-term effects of fire on soil carbon and nutrient storage, or whether fire-driven nutrient losses limit plant productivity. Here we analyse data from 48 sites in savanna grasslands, broadleaf forests and needleleaf forests spanning up to 65 years, during which time the…
Publication Type: Journal Article
Tamm Review: Shifting global fire regimes: Lessons from reburns and research needs
Year: 2017
Across the globe, rising temperatures and altered precipitation patterns have caused persistent regional droughts, lengthened fire seasons, and increased the number of weather-driven extreme fire events. Because wildfires currently impact an increasing proportion of the total area burned, land managers need to better understand reburns – in which previously burned areas can modify the patterns and severity of subsequent fires. For example, knowing how long past fire boundaries can function as barriers to fire spread may empower decision-makers to manage some wildfires as large-scale fuel…
Publication Type: Journal Article