Fire Ecology & Effects
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In sagebrush ecosystems invasion of annual exotics and expansion of pinyon and juniper are altering fire regimes and resulting in large-scale ecosystem transformations. Management treatments aim to increase resilience to disturbance and enhance resistance to invasive species by reducing woody fuels and increasing native perennial herbaceous species. This study used Sagebrush Steppe Treatment Evaluation Project data to test predictions on effects of fire vs. mechanical treatments on resilience and resistance for three site types. Warm (mesic) WY Shrub and WY PJ sites had lower resistance to annual exotics than cool (frigid to cool frigid) Mtn PJ sites. In WY shrub, fire and sagebrush mowing had similar effects on shrub cover and, thus, on perennial native herbaceous and exotic cover. In WY PJ and Mtn PJ, effects were greater for fire than cut-and-leave treatments and with high tree cover in general because most woody vegetation was removed increasing resources for other functional groups. In WY shrub, about 20% pretreatment perennial native herb cover was necessary to prevent increases in exotics after treatment. Cooler and moister WY PJ and especially Mtn PJ were more resistant to annual exotics, but perennial native herb cover was still required for site recovery. We use our results to develop state and transition models that illustrate how resilience and resistance influence vegetation dynamics and management options.
Want to beef-up your library? You can request the following resources in hard copy from Génie (listed in order of most recent publication date). You can also add them to your electronic library, just follow the links for downloads.
Fire patterns in piñon and juniper land cover types in the Semiarid Western United States from 1984 through 2013, 2018. RMRS-GTR-372
Restoration handbook for sagebrush steppe ecosystems with emphasis on greater sage-grouse habitat—Part 3. Site level restoration decisions, 2018. USGS Circular 1426
Science framework for conservation and restoration of the sagebrush biome: Linking the Department of the Interior’s Integrated Rangeland Fire Management Strategy to long-term strategic conservation actions, 2017. RMRS-GTR-360
Pocket Guide to Sagebrush Birds, reprint, 2017. A partnership between Rocky Mountain Bird Observatory and PRBO Conservation Science
Pocket Guide to Sagebrush, reprint, 2017. Made possible by USU, NRCS, USFS, BLM, PRBO Conservation Science, NDOW, GBFSE
Ecohydrologic impacts of rangeland fire on runoff and erosion: A literature synthesis, 2016. RMRS-GTR-351
Using resilience and resistance concepts to manage threats to sagebrush ecosystems, Gunnison sage-grouse, and Greater sage-grouse in their eastern range: A strategic multi-scale approach, 2016. RMRS-GTR-356
A field guide for rapid assessment of post-wildfire recovery potential in sagebrush and pinon-juniper ecosystems in the Great Basin: Evaluating resilience to disturbance and resistance to invasive annual grasses and predicting vegetation response, 2015. RMRS-GTR-338
A review of fire effects on vegetation and soils in the Great Basin Region: Response and site characteristics, 2013. RMRS-GTR-308
The Reburn Project was motivated by a need to better understand wildfires as a type of fuel reduction treatment and to assess the impacts of fire suppression on forested landscapes. The original JFSP task statement (Influence of past wildfires on wildfire behavior, effects, and management) was created to inform the National Cohesive Wildland Fire Management Strategy and to address how past wildfires influence subsequent wildfire spread and severity as well as to evaluate how past wildfires may support different fire management strategies. Our study focused on three study areas, located in the inland Pacific Northwest, central Idaho and interior British Columbia. Each study area was centered on a recent, large wildfire event in montane, forested landscapes.We first evaluated fire-on-fire interactions between past wildfires and subsequent large fire events (see Stevens-Rumann et al. 2016). Next, we created a landscape fire simulation tool that allowed us to explore the impact of fire management on the patterns of forest vegetation and fuels across landscapes. To do this, we created an iterative tool that uses historical ignition and weather data to evaluate potential burn mosaics compared to actual pre-wildfire landscapes under different wildfire management strategies.
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In this issue:
- Wildfire and SageSTEP research: An inevitable collision
- Treatment longevity and changes in surface fuel loads after pinyon-juniper mastication
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Here, we explore the drivers of high-severity fire for forested ecoregions in the western US over the period 2002–2015. We 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. We 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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In the Deschutes National Forest, researchers with the USFS Pacific Northwest Research Station, Oregon State University, and Kansas State University conducted a study to compare the effects of low-intensity and high-intensity burns on soil organisms and nutrients. The high-intensity burns were simulated by burning “mega-logs,” a proxy for naturally occurring large downed wood. They established 12 sites and collected pre- and postburn soil samples and continuous temperature recordings during the fire. As expected, the soil on the mega-log sites experienced intense heating. High temperatures penetrated 4 inches below the surface but no farther than 12 inches, and soil carbon and organic matterderived nutrients were volatized. There was also a substantial loss of nearly all the existing microbial communities. Within one week, however, fungi had returned; ascomycete fungi, such as morels, dominated the sites. Ponderosa pine seedlings were colonized by ectomycorrhizal fungi within four months.
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Mixed severity wildfires burn large areas in western North America forest ecosystems in most years and this is expected to continue or increase with climate change. Little is understood about vegetation recovery and changing fuel conditions more than a decade post-fire because it exceeds the duration of most studies of fire effects. We measured plant species composition, conifer seedling regeneration, fuel loads, and ground cover at 15 wildfires that burned 9-15 years previous in five western U.S. vegetation types distributed across eight states including Alaska.
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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.