Fire Ecology & Effects
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Low-severity wildland fires and prescribed burns have long been presumed by scientists and resource managers to be harmless to soils, but this may not be the case, new research shows. According to two new studies, low-severity burns cause damage to soil structure and organic matter in ways that are not immediately apparent after a fire.
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This report contains descriptions of USGS sage-grouse and sagebrush ecosystem research projects that are ongoing or were active during 2018 and is organized into five thematic areas: Fire, Invasive Species, Restoration, Sagebrush, Sage-Grouse, and Other Sagebrush-Associated Species; and Climate and Weather.
The ecological effects of wildland fire – also termed the fire severity – are often highly heterogeneous in space and time. This heterogeneity is a result of spatial variability in factors such as fuel, topography, and climate (e.g. a map of mean annual temperature). However, temporally variable factors such as daily weather and climatic extremes (e.g. an unusually warm year) also may play a key role. We conducted a study in which statistical models were produced describing fire severity as a function of live fuel, topography, climate, and fire weather. On average, live fuel was the most influential factor driving fire severity, followed by fire weather, climate, and topography. The statistical models we produced were then used to generate maps depicting the probability of high-severity fire, if a fire were to occur, for several ecoregions in the western US. These maps can potentially be used by land management agencies to prioritize hazardous fuel reduction treatments. This webinar pertains to all mountainous regions of the western US but will slightly emphasize the southwestern US.
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This study found that live fuel, on average, was the most important factor driving high-severity fire among ecoregions (average relative influence = 53.1%) and was the most important factor in 14 of 19 ecoregions. Fire weather was the second most important factor among ecoregions (average relative influence = 22.9%) and was the most important factor in five ecoregions. Climate (13.7%) and topography (10.3%) were less influential. The study also predicted the probability of high-severity fire, were a fire to occur, using recent (2016) satellite imagery to characterize live fuel for a subset of ecoregions in which the model skill was deemed acceptable (n = 13). These ‘wall-to-wall’ gridded ecoregional maps provide relevant and up-to-date information for scientists and managers who are tasked with managing fuel and wildland fire.
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Study results indicate that burning during fescue establishment can prevent proliferation, but burning two years later when fescue had reached peak abundance was ineffective. All three burn treatments that suppressed fescue subsequently enhanced C4 grass production. Researchers suggest that rangeland managers be aware of the potential for sixweeks fescue germination and establishment during warm, wet winters that follow drought years, and consider the use of dormant-season prescribed fire to adaptively reduce negative impacts on forage production.
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This study 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. Fire rotations were within reported historical ranges for sagebrush ecosystems and decreased over time. Also, fire number or fire size increased for the Southern Rocky Mountain and Southern Intermountain geographic regions. Across the study area, spatio-temporal patterns in fire regimes for piñon and juniper land cover types were similar to those for other land cover types. Careful monitoring of longer term trends in fire activity and the interacting effects of invasive annual grasses, bark beetles, and climate change is needed to access the dynamics of piñon and juniper land cover types and evaluate the efficacy of management treatments in piñon and juniper land cover types.
This project and it’s associated resources, can be accessed here.
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While news headlines were quick to capture the “cost” of firefighting, suppression represents only a fraction of the true cost of wildfire. There are huge impacts to air quality and health, school athletics, travel and tourism, employment and the economy, transportation, and iconic Oregon economic sectors such as the state’s wine and timber industries. No single state agency is charged with documenting these costs, so the Oregon Forest Resources Institute set out to gather what information is currently available, from media reports, individual interviews and hard-nosed research.
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Abstracts of Recent Papers on Range Management in the West. Prepared by Charlie Clements, Rangeland Scientist, USDA Agricultural Research Service, Reno, NV.
This webinar describes:
- The long-term (17-26 year) post-fire accumulation in fuel loads and resultant potential fire behavior where historical prefire and immediate postfire data exists in Wyoming and Basin big sagebrush communities.
- Fuel loads accumulation and structure along a time-since-fire. chronosequence in Wyoming, mountain, and low sagebrush ecosystems
- The fuels and reburn potential in once and twice burned Basin big sagebrush plant communities.
- Plant community change 17 years post fire in Wyoming big sagebrush ecosystems.
Presented by: Lisa Ellsworth, Oregon State University.