Fire History
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This study compared fire size, seasonality, and environmental conditions (e.g., wind speed, fuel moisture, biomass, vegetation type) of large human- and lighting-started fires that required a suppression response. Mean large fire size varied by three orders of magnitude: from 1 to 10 ha in the Northeast vs. >1000 ha in the West. Humans ignited four times as many large fires as lightning, and were the dominant source of large fires in the eastern and western U.S. (starting 92% and 65% of fires, respectively). Humans started 80,896 large fires in seasons when lightning-ignited fires were rare. Large human-started fires occurred in locations and months of significantly higher fuel moisture and wind speed than large lightning-started fires.
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This study evaluated spatio-temporal patterns of fire in piñon and juniper land cover types from the National Gap Analysis Program using Monitoring Trends in Burn Severity (MTBS 2016) data (1984 through 2013) for Northern and Southern Intermountain and Central and Southern Rocky Mountain geographic regions. It also examined differences in total area burned, fire rotation, fire size, fire number, and fire season among: 1) the four geographic regions; 2) the EPA level III ecoregions that occur within each geographic region; and 3) the piñon and juniper land cover types (woodlands, savannas, and shrublands) and other land cover types that occur within each geographic region and level III ecoregion. We found that area burned during the 30-year period, number of fires each year, and fire size followed a strong geographic pattern: Northern Intermountain > Southern Intermountain > Southern Rocky Mountain > Central Rocky Mountain. Area burned within piñon and juniper land cover types increased significantly during the 30-year period across the study area overall and for each geographic region, except the Southern Intermountain.
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We examined the effect of livestock grazing and previous wildfire events on fuel load in southeastern Idaho as part of a wildfire risk-livestock interaction study. Fuel load was estimated using ordinal fuel load classes at 128 sample sites stratified by current livestock grazing and documented wildfire occurrence (1939-2000). Fifty-nine percent of previous wildfire sites had a documented fire within the past 2 years. Livestock grazing was the most effective means to reduce fuel load compared to recent wildfire and livestock grazing with previous wildfire. Livestock grazing provides a viable management tool for fuel load reduction prescriptions that avoids the negative effect of extreme fire intensity where fuel load is high.
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Paleovegetation studies show that even prior to anthropogenic influence, sage steppe communities were dynamic, and in some cases, susceptible to replacement by other vegetation communities (including forests) under changing climatic conditions.
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This document includes scientist contributions and group recommendations that came from the Great Basin Wildfire Forum held at the University of Nevada in September of 2007. In the first section, the editors provide background and overview of the major issues of the Great Basin as they relate to the wildfire forum discussions. The next section is an edited version of the individual contributions of the scientists based on their oral presentations and written contributions.
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The FEIS database provides access to more than 1,200 species reviews, 150 fire studies, and is now producing fire regime syntheses. This suite of products provides information on plant, lichen, and wildlife species’ life history, ecology, and relationship to fire and detailed descriptions of site characteristics, burning conditions, fire behavior, and fire effects. This spatially searchable database was developed by the USDA-FS, Rocky Mountain Research Station, Fire Sciences Laboratory, Missoula, Montana.
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This study evaluated how divergence from historic (pre-Euroamerican settlement) fire frequencies due to a century of fire suppression influences rates of high-severity fire in five forest types in California. With some variation, results suggest that fires in forest types characterized by fuel-limited fire regimes (e.g., yellow pine and mixed conifer forest) tend to burn with greater proportions of high-severity fire as either time since last fire or the mean modern fire return interval (FRI) increases.
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In this study, researchers compiled landscape-scale evidence of historical fire severity patterns in the ponderosa pine and mixed-conifer forests from published literature sources and stand ages available from the Forest Inventory and Analysis program in the USA. The consensus from this evidence is that the traditional reference conditions of low-severity fire regimes are inaccurate for most forests of western North America. Instead, most forests appear to have been characterized by mixed-severity fire that included ecologically significant amounts of weather-driven, high-severity fire.
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This research brief reports that the cessation of fire use by Indians and a shift to climatic conditions less favorable to fire are both explanations for decreased fire frequency over the past century and a half in the southern Great Basin and Mojave desert ecotone.
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This report found that big sagebrush recovery following fire over a broad regional scale suggests an average recovery time of 25 to 35+ years. However, there was much variation in recovery rate associated with the timing of precipitation relative to the particular fire event. We found that precipitation in the pre-fire growing season was positively related to post-fire recovery of mountain big sagebrush, and that precipitation in the late winter following fire was similarly positively related to recovery rate.