Research Database
Displaying 161 - 180 of 194
The role of defensible space for residential structure protection during wildfires
Year: 2014
With the potential for worsening fire conditions, discussion is escalating over how to best reduce effects on urban communities. A widely supported strategy is the creation of defensible space immediately surrounding homes and other structures. Although state and local governments publish specific guidelines and requirements, there is little empirical evidence to suggest how much vegetation modification is needed to provide significant benefits. We analysed the role of defensible space by mapping and measuring a suite of variables on modern pre-fire aerial photography for 1000 destroyed and…
Publication Type: Journal Article
Contrasting Spatial Patterns in Active-Fire and Fire- Suppressed Mediterranean Climate Old-Growth Mixed Conifer Forests
Year: 2014
In Mediterranean environments in western North America, historic fire regimes in frequent-fire conifer forests are highly variable both temporally and spatially. This complexity influenced forest structure and spatial patterns, but some of this diversity has been lost due to anthropogenic disruption of ecosystem processes, including fire. Information from reference forest sites can help management efforts to restore forests conditions that may be more resilient to future changes in disturbance regimes and climate. In this study, we characterize tree spatial patterns using four-ha stem maps…
Publication Type: Journal Article
Dry forest resilience varies under simulated climate-management scenarios in a central Oregon, USA landscape
Year: 2014
Determining appropriate actions to create or maintain landscapes resilient to climate change is challenging because of uncertainty associated with potential effects of climate change and their interactions with land management. We used a set of climate informed state-and-transition models to explore the effects of management and natural disturbances on vegetation composition and structure under different future climates. Models were run for dry forests of central Oregon under a fire suppression scenario (i.e., no management other than the continued suppression of wildfires) and an active…
Publication Type: Journal Article
Briefing: Climate and Wildfire in Western U.S. Forests
Year: 2014
Wildfire in western U.S. federally managed forests has increased substantially in recent decades, with large (>1000 acre) fires in the decade through 2012 over five times as frequent (450 percent increase) and burned area over ten times as great (930 percent increase) as the 1970s and early 1980s. These changes are closely linked to increased temperatures and a greater frequency and intensity of drought. Projected additional future warming implies that wildfire activity may continue to increase in western forests. However, the interaction of changes in climate, fire and other disturbances…
Publication Type: Conference Proceedings
Correlations between components of the water balance and burned area reveal insights for predicting forest fire area in the southwest United States
Year: 2014
We related measurements of annual burned area in the southwest United States during 1984–2013 to records of climate variability. Within forests, annual burned area correlated at least as strongly with spring–summer vapour pressure deficit (VPD) as with 14 other drought-related metrics, including more complex metrics that explicitly represent fuel moisture. Particularly strong correlations with VPD arise partly because this term dictates the atmospheric moisture demand. Additionally, VPD responds to moisture supply, which is difficult to measure and model regionally due to complex…
Publication Type: Journal Article
Mathematical model and sensor development for measuring energy transfer from wildland fires
Year: 2014
Current practices for measuring high heat flux in scenarios such as wildland forest fires use expensive, thermopile-based sensors, coupled with mathematical models based on a semi-infinite-length scale. Although these sensors are acceptable for experimental testing in laboratories, high error rates or the need for water cooling limits their applications in field experiments. Therefore, a one-dimensional, finite-length scale, transient-heat conduction model was developed and combined with an inexpensive, thermocouple-based rectangular sensor, to create a rapidly deployable, non-cooled sensor…
Publication Type: Journal Article
Severity of an uncharacteristically large wildfire, the Rim Fire, in forests with relatively restored frequent fire regimes
Year: 2014
The 2013 Rim Fire, originating on Forest Service land, burned into old-growth forests within Yosemite National Park with relatively restored frequent-fire regimes (¡Ý2 predominantly low and moderate severity burns within the last 35 years). Forest structure and fuels data were collected in the field 3-4 years before the fire, providing a rare chance to use pre-existing plot data to analyze fire effects. We used regression tree and random forests analysis to examine the influence of forest structure, fuel, fire history, topographic and weather conditions on observed fire severity in the Rim…
Publication Type: Journal Article
Pre-wildfire fuel reduction treatments result in more resilient forest structure a decade after wildfire
Year: 2013
Increasing size and severity of wildfires have led to an interest in the effectiveness of forest fuels treatments on reducing fire severity and post-wildfire fuels. Our objective was to contrast stand structure and surface fuel loadings on treated and untreated sites within the 2002 Rodeo-Chediski Fire area. Data from 140 plots on seven paired treated-untreated sites indicated that pre-wildfire treatments reduced fire severity compared with untreated sites. In 2011, coarse woody debris loading (woody material.7.62 cm in diameter) was 257% higher and fine woody debris (woody material,7.62 cm)…
Publication Type: Journal Article
Wildland Fire management: Are actively managed forests more resilient than passively managed forests?
Year: 2013
Large areas of federal lands in the western states are currently at high risk of severe wildfire and have many insect and disease problems, indicating a significant decline in forest health and resilience. Although research studies have not been done that would measure whether actively managed forests are more resilient to wildfires than passively managed forests, results from studies of hazardous fuels treatment effectiveness and the economic benefits from avoided costs of future wildfire suppression due to fuels treatment can be used to support an affirmative reply to the question. If a…
Publication Type: Report
Modelling conditional burn probability patterns for large wildland fires
Year: 2013
We present a technique for modelling conditional burn probability patterns in two dimensions for large wildland fires. The intended use for the model is strategic program planning when information about future fire weather and event durations is unavailable and estimates of the average probabilistic shape and extent of large fires on a landscape are needed. To model average conditional burn probability patterns, we organised historical fire data from Yellowstone National Park, USA, into a set of grids; one grid per fire. We captured various spatial relationships inherent in the gridded data…
Publication Type: Journal Article
Assessing forest vegetation and fire simulation model performance after the Cold Springs wildfire, Washington, USA
Year: 2013
Given that resource managers rely on computer simulation models when it is difficult or expensive to obtain vital information directly, it is important to evaluate how well a particular model satisfies applications for which it is designed. The Forest Vegetation Simulator (FVS) is used widely for forest management in the US, and its scope and complexity continue to increase. This paper focuses on the accuracy of estimates made by the Fire and Fuels Extension (FFE-FVS) predictions through comparisons between model outputs and measured post-fire conditions for the Cold Springs wildfire and on…
Publication Type: Journal Article
Relationships between climate and macroscale area burned in the western United States
Year: 2013
Increased wildfire activity (e.g. number of starts, area burned, fire behaviour) across the western United States in recent decades has heightened interest in resolving climate–fire relationships. Macroscale climate–fire relationships were examined in forested and non-forested lands for eight Geographic Area Coordination Centers in the western United States, using area burned derived from the Monitoring Trends in Burn Severity dataset (1984–2010). Fire-specific biophysical variables including fire danger and water balance metrics were considered in addition to standard climate variables of…
Publication Type: Journal Article
Restoring forest resilience: From reference spatial patterns to silvicultural prescriptions and monitoring
Year: 2013
Stand-level spatial pattern influences key aspects of resilience and ecosystem function such as disturbance behavior, regeneration, snow retention, and habitat quality in frequent-fire pine and mixed-conifer forests. Reference sites, from both pre-settlement era reconstructions and contemporary forests with active fire regimes, indicate that frequent-fire forests are complex mosaics of individual trees, tree clumps, and openings. There is a broad scientific consensus that restoration treatments should seek to restore this mosaic pattern in order to restore resilience and maintain ecosystem…
Publication Type: Journal Article
Allowing a wildfire to burn: estimating the effect on future suppression costs
Year: 2013
Where a legacy of aggressive wildland fire suppression has left forests in need of fuel reduction, allowing wildland fire to burn may provide fuel treatment benefits, thereby reducing suppression costs from subsequent fires. The least-cost-plus-net-value-change model of wildland fire economics includes benefits of wildfire in a framework for evaluating suppression options. In this study, we estimated one component of that benefit – the expected present value of the reduction in suppression costs for subsequent fires arising from the fuel treatment effect of a current fire. To that end, we…
Publication Type: Journal Article
The leaf-area shrinkage effect can bias paleoclimate and ecology research
Year: 2012
Premise of the Study: Leaf area is a key trait that links plant form, function, and environment. Measures of leaf area can be biased because leaf area is often estimated from dried or fossilized specimens that have shrunk by an unknown amount. We tested the common assumption that this shrinkage is negligible. Methods: We measured shrinkage by comparing dry and fresh leaf area in 3401 leaves of 380 temperate and tropical species and used phylogenetic and trait-based approaches to determine predictors of this shrinkage. We also tested the effects of rehydration and simulated fossilization on…
Publication Type: Journal Article
The Age of Western Wildfires
Year: 2012
The 2012 wildfire season isn’t over yet, but already this year is shaping up to be the one of the worst on record in the American West. According to the National Interagency Fire Center, with nearly two months still to go in the fire season, the total area already burned this year is 30 percent more than in an average year, and fires have consumed more than 8.6 million acres, an area larger than the state of Maryland. Yet, what defines a “typical” wildfire year in the West is changing. In the past 40 years, rising spring and summer temperatures, along with shrinking winter snowpack, have…
Publication Type: Report
Multiple successional pathways and precocity in forest development: can some forests be born complex?
Year: 2012
Background. In forests subject to stand-replacing disturbances, conventional models of succession typically overlook early-seral stages as a simple re- organization/establishment period. These models treat structural development in essentially ‘relay floristic’ terms, with structural complexity (three-dimensional heterogeneity) developing primarily in old-growth stages, only after a closed-canopy ‘self-thinning’ phase and subsequent canopy gap formation. However, is it possible that early-successional forests can sometimes exhibit spatial complexity similar to that in old-growth forests – i.e…
Publication Type: Journal Article
Health Effects of Wildland Fire Smoke: Insight from Public Health Science Studies
Year: 2012
Due to the composition and dispersion of wildland fire smoke, particulate matter is the principal pollutant of public health concern. Effects will vary based on the source of smoke but predominantly impact local communities in the same way. Studies of the effects of PM from non-fire sources show that long-term exposure can reduce lung function and cause the development of chronic bronchitis. Short-term exposure (hours or days), typical of wildland fire events, can aggravate lung disease, leading to asthma attacks and acute bronchitis. These effects can also increase the susceptibility to…
Publication Type: Report
Temporal dynamics and decay of coarse wood in early seral habitats of dry-mixed conifer forests in Oregon’s Eastern Cascades
Year: 2012
Early seral forest habitats are increasingly valued for the unique structural resources they provide in many western US forests. Coarse woody detritus (CWD) are a significant feature of this developmental stage and are highly dynamic, suggesting these environments exhibit temporally diverse structural conditions prior to forest canopy closure. In dry-mixed conifer forests, snags are hypothesized to decay slower than logs making long-term dynamics in these forests dependent on snag fall, breakage and the decay rates of both standing and surface CWD. We estimated snag fall and breakage rates…
Publication Type: Journal Article
Atmospheric Interactions with Wildland Fire Behaviour II. Plume and Vortex Dynamics
Year: 2012
This paper is the second of two reviewing scientific literature from 100 years of research addressing interactions between the atmosphere and fire behaviour. These papers consider research on the interactions between the fuels burning at any instant and the atmosphere, and the interactions between the atmosphere and those fuels that will eventually burn in a given fire. The first paper reviews the progression from the surface atmospheric properties of temperature, humidity and wind to horizontal and vertical synoptic structures and ends with vertical atmospheric profiles. This second paper…
Publication Type: Journal Article