Research Database
Displaying 181 - 200 of 229
Fire severity and tree regeneration following bark beetle outbreaks: the role of outbreak stage and burning conditions
Year: 2014
The degree to which recent bark beetle (Dendroctonus ponderosae) outbreaks may influence fire severity and postfire tree regeneration is of heightened interest to resource managers throughout western North America, but empirical data on actual fire effects are lacking. Outcomes may depend on burning conditions (i.e., weather during fire), outbreak severity, or intervals between outbreaks and subsequent fire. We studied recent fires that burned through green-attack/red-stage (outbreaks <3 years before fire) and gray-stage (outbreaks 3–15 years before fire) subalpine forests dominated by…
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
Climate, fire size, and biophysical setting control fire severity and spatial pattern in the northern Cascade Range, USA
Year: 2014
Warmer and drier climate over the past few decades has brought larger fire sizes and increased annual area burned in forested ecosystems of western North America, and continued increases in annual area burned are expected due to climate change. As warming continues, fires may also increase in severity and produce larger contiguous patches of severely burned areas. We used remotely sensed burn-severity data from 125 fires in the northern Cascade Range of Washington, USA, to explore relationships between fire size, severity, and the spatial pattern of severity. We examined relationships between…
Publication Type: Journal Article
Clearcutting and high severity wildfire have comparable effects on growth of direct-seeded interior Douglas-fir
Year: 2014
The degree to which harvesting can achieve comparable beneficial effects to wildfire on seedling establishment is a key factor in understanding regeneration dynamics in dry interior forest ecosystems. We compared the capacity of harvesting versus wildfire to support establishment of directly-seeded interior Douglas-fir over a three-year period in the interior Douglas-fir biogeoclimatic zone of British Columbia. The mixed-severity McLure Fire of August 2003 affected over 26,000 hectares in the central British Columbia, Canada. Within the fire-affected area, we assessed growth performance in…
Publication Type: Journal Article
A synthesis of post-fire Burned Area Reports from 1972 to 2009 for western US Forest Service lands: trends in wildfire characteristics and post-fire stabilisation treatments and expenditures
Year: 2014
Over 1200 post-fire assessment and treatment implementation reports from four decades (1970s–2000s) of western US forest fires have been examined to identify decadal patterns in fire characteristics and the justifications and expenditures for the post-fire treatments. The main trends found were: (1) the area burned by wildfire increased over time and the rate of increase accelerated after 1990; (2) the proportions of burned area assessed as low, moderate and high burn severity likely have remained fairly constant over time, but the use of satellite imagery that began c. 2000 increased the…
Publication Type: Journal Article
Landscape restoration of a forest with a historically mixed-severity fire regime: What was the historical landscape pattern of forest and openings?
Year: 2014
Forest management of dry forests in the western US that historically experienced mixed-severity fire regimes is increasingly focused on landscape-scale restoration. However, this restoration effort is constrained by historic range of variation (HRV) reference conditions that lack information concerning the spatial configuration of these forests at intermediate scales (approximately 0.01–100 ha). I used reconstruction methods to map historical (1860) pattern of ponderosa pine-Douglas-fir forests along twenty 1 km long transects on Colorado’s Front Range and compared pre-settlement opening and…
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
Vegetation Recovery in Slash-Pile Scars Following Conifer Removal in a Grassland-Restoration Experiment
Year: 2014
A principal challenge to restoring tree-invaded grasslandsis the removal of woody biomass. Burning of slash pilesto reduce woody residues from forest restoration practicesgenerates intense, prolonged heating, with adverse effectson soils and vegetation. In this study, we examined vegetationresponses to pile burning following tree removalfrom conifer-invaded grasslands of the Oregon Cascades.We quantified the longevity and magnitude of fire effectsby comparing ground conditions and the cover and richnessof plant species in burn-scar centers (higher-intensityfire) and edges (lower-intensity…
Publication Type: Journal Article
The relationship of post-fire white ash cover to surface fuel consumption
Year: 2013
White ash results from the complete combustion of surface fuels, making it a logically simple retrospective indicator of surface fuel consumption. However, the strength of this relationship has been neither tested nor adequately demonstrated with field measurements. We measured surface fuel loads and cover fractions of white ash and four other surface materials (green vegetation, brown non-photosynthetic vegetation, black char and mineral soil) immediately before and after eight prescribed fires in four disparate fuelbed types: boreal forest floor, mixed conifer woody slash, mixed conifer…
Publication Type: Journal Article
Using native annual plants to restore post-fire habitats in western North America
Year: 2013
Increasing fire frequencies and uncharacteristic severe fires have created a need for improved restoration methods across rangelands in western North America. Traditional restoration seed mixtures of native perennial mid- to late-seral plant species may not be suitable for intensely burned sites that have been returned to an early-seral condition. Under such conditions, native annual plant species are likely to be more successful at becoming established and competing with exotic annual plant species, such as Bromus tectorum L., for resources. We used a field study in Colorado and Idaho, USA,…
Publication Type: Journal Article
Regional constraints to biological nitrogen fixation in post-fire forest communities
Year: 2013
Biological nitrogen fixation (BNF) is a key ecological process that can restore nitrogen (N) lost in wildfire and shape the pace and pattern of post-fire forest recovery. To date, there is limited information on how climate and soil fertility interact to influence different pathways of BNF in early forest succession. We studied asymbiotic (forest floor and soil) and symbiotic (the shrub Ceanothus integerrimus) BNF rates across six sites in the Klamath National Forest, California, USA. We used combined gradient and experimental phosphorus (P) fertilization studies to explore cross-site…
Publication Type: Journal Article
Previous Fires Moderate Burn Severity of Subsequent Wildland Fires in Two Large Western US Wilderness Areas
Year: 2013
Wildland fire is an important natural process in many ecosystems. However, fire exclusion has reduced frequency of fire and area burned in many dry forest types, which may affect vegetation structure and composition, and potential fire behavior. In forests of the western U.S., these effects pose a challenge for fire and land managers who seek to restore the ecological process of fire to ecosystems. Recent research suggests that landscapes with unaltered fire regimes are more ‘‘self-regulating’’ than those that have experienced fire-regime shifts; in self-regulating systems, fire size and…
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
Climate stress increases forest fire severity across the western United States
Year: 2013
Pervasive warming can lead to chronic stress on forest trees, which may contribute to mortality resultingfrom fire-caused injuries. Longitudinal analyses of forest plots from across the western US show that highpre-fire climatic water deficit was related to increased post-fire tree mortality probabilities. This relationshipbetween climate and fire was present after accounting for fire defences and injuries, and appeared to influencethe effects of crown and stem injuries. Climate and fire interactions did not vary substantially acrossgeographical regions, major genera and tree sizes. Our…
Publication Type: Journal Article
Fire-mediated pathways of stand development in Douglas-fir/ western hemlock forests of the Pacific Northwest, USA
Year: 2013
Forests dominated by Douglas-fir and western hemlock in the Pacific Northwest of the United States have strongly influenced concepts and policy concerning old-growth forest conservation. Despite the attention to their old-growth characteristics, a tendency remains to view their disturbance ecology in relatively simple terms, emphasizing infrequent, stand-replacing (SR) fire and an associated linear pathway toward development of those old-growth characteristics. This study uses forest stand- and age-structure data from 124 stands in the central western Cascades of Oregon to construct a…
Publication Type: Journal Article
Fuel Treatments and Fire Severity: A Meta-Analysis
Year: 2013
We employed meta-analysis and information theory to synthesize findings reported in the literature on the effects of fuel treatments on subsequent fire intensity and severity. Data were compiled from 19 publications that reported observed fire responses from 62 treated versus untreated contrasts. Effect sizes varied widely and the most informative grouping of studies distinguished three vegetation types and three types of fuel treatment. The resultant meta-analytic model is highly significant (p<0.001) and explains 78% of the variability in reported observations of fuel treatment…
Publication Type: Report
Influence of climate and environment on post-fire recovery of mountain sagbrush
Year: 2013
In arid and semi-arid landscapes around the world, wildfire plays a key role in maintaining species diversity. Dominant plant associations may depend upon particular fire regime characteristics for their persistence. Mountain shrub communities in high-elevation landscapes of the Intermountain West, USA, are strongly influenced by the post-fire recovery dynamics of the obligate-seeding shrub, mountain big sagebrush (Artemisia tridentata Nutt. ssp. vaseyana [Rydb.] Beetle). This species is a short-distance disperser with a short-lived seedbank, leading to highly variable post-fire recovery…
Publication Type: Journal Article
Alteration and Recovery of Slash Pile Burn Sites in the Restoration of a Fire-Maintained Ecosystem
Year: 2012
Restoration practices incorporating timber harvest (e.g. to remove undesirable species or reduce tree densities) may generate unmerchantable wood debris that is piled and burned for fuel reduction. Slash pile burns are common in longleaf pine ecosystem restoration that involves hardwood removal before reintroduction of frequent prescribed fire. In this context, long-lasting effects of slash pile burns may complicate restoration outcomes due to unintended alterations to vegetation, soils, and the soil seed bank. In this study, our objectives were to (1) examine alterations to the soil seed…
Publication Type: Journal Article
Meta-analysis of avian and small-mammal response to fire severity and fire surrogate treatments in US fire-prone forests
Year: 2012
Management in fire-prone ecosystems relies widely upon application of prescribed fire and/or fire surrogate (e.g., forest thinning) treatments to maintain biodiversity and ecosystem function. Recently, published literature examining wildlife response to fire and fire management has increased rapidly. However, none of this literature has been synthesized quantitatively, precluding assessment of consistent patterns of wildlife response among treatment types. Using meta- analysis, we examined the scientific literature on vertebrate demographic responses to burn severity (low/moderate, high),…
Publication Type: Journal Article