Post-fire Environment & Management
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In this webinar, Dr. Kimberley Davis examined the effects of climate on post-fire conifer regeneration and subsequent seedling and tree growth. She and her colleagues focused on lower elevation ponderosa pine and Douglas-fir forests to identify the climate conditions that are necessary for these species to regenerate and grow following fire. Their study found that changing climate conditions are making it increasingly difficult for tree seedlings to regenerate after fire, suggesting that fires may cause conversions to non-forest vegetation in the hottest and driest areas. Dr. Davis also discussed how disturbances that reduce canopy cover, such as wildfire, may alter microclimate conditions.
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This presentation will focus on findings from JFSP-supported graduate research on post-fire conifer establishment following recent wildfires in eastern Oregon’s Blue Mountains. Given shifting climate and wildfire regimes, managers and researchers seek information on forest resilience and recovery trajectories. Understanding establishment and growth rates post-fire is pertinent both to fuels management planning, in cases of overabundant regeneration, as well as to decisions surrounding replanting for sites with limited post-fire regeneration. The presentation will summarize current knowledge on the relative influence of site-level versus climatic factors affecting regeneration in western North America, and present data from the Blue Mountains ecoregion.
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Fire refugia and the seed sources they contain fostered tree regeneration in severely burned patches. Management practices that reduce refugia within post-fire landscapes may negatively influence essential forest recovery processes.
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Ephemeral snowpacks, or those that persist for < 60 continuous days, are challenging to observe and model because snow accumulation and ablation occur during the same season. This has left ephemeral snow understudied, despite its widespread extent. Using 328 site years from the Great Basin, we show that ephemeral snowmelt causes a 70-days-earlier soil moisture response than seasonal snowmelt. In addition, deep soil moisture response was more variable in areas with seasonal snowmelt. To understand Great Basin snow distribution, we used MODIS and Snow Data Assimilation System (SNODAS) data to map snow extent. Estimates of maximum continuous snow cover duration from SNODAS consistently overestimated MODIS observations by >25 days in the lowest (<1500 m) and highest (>2500 m) elevations. During this time period snowpack was highly variable. The maximum seasonal snow cover during water years 2005–2014 was 64 % in 2010 and at a minimum of 24 % in 2014. We found that elevation had a strong control on snow ephemerality, and nearly all snowpacks over 2500 m were seasonal except those on south-facing slopes. Additionally, we used SNODAS-derived estimates of solid and liquid precipitation, melt, sublimation, and blowing snow sublimation to define snow ephemerality mechanisms. In warm years, the Great Basin shifts to ephemerally dominant as the rain–snow transition increases in elevation. Given that snow ephemerality is expected to increase as a consequence of climate change, physics-based modeling is needed that can account for the complex energetics of shallow snowpacks in complex terrain. These modeling efforts will need to be supported by field observations of mass and energy and linked to finer remote sensing snow products in order to track ephemeral snow dynamics.
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Of our estimated 3.7 Mkm2 of rangeland in the continental US and Alaska, an average of 38 000 km2 burned per year between 2008 and 2017. To highlight the role of soils in fire ecology, we present 1) a conceptual framework explaining why soil information can be useful for fire models, 2) a comprehensive suite of literature examples that used soil property information in traditional soil survey for predicting wildfire, and 3) specific examples of how more detailed soil information can be applied for pre- and post-fire decisions.
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This study evaluated the effect of herbicide (imazapic) applied in the first winter or second fall after the 113,000 ha Soda wildfire on the target exotic annual grasses and also key non-target components of the plant community. Cover of exotic annual grass cover, but not of deep-rooted perennial bunchgrass, was less where imazapic had been applied, whereas more variability was evident in the response of Sandberg bluegrass and seeded shrubs and forbs. Regression-tree analysis of the subset of plots measured both before and after the second fall application revealed greater reductions of exotic annual grass cover in places where their cover was <42% before spraying. Otherwise, imazapic effects did not vary with the landscape factors we analyzed.
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To assess the effects of aerial and drill seeding on plant community trajectories, fuel composition, and fire regimes, this study collected geospatial datasets spanning 209,000 ha of sagebrush steppe on BLM land in southern Idaho. In the field, 68 sites were sampled for fuel and plant community composition in 2014 and 2015 across areas that had burned 1-6 times and had no, aerial, drill, or aerial + drill seeding. The study found that 1) fire and rehabilitation shaped plant communities, 2) drill seeding after multiple fires in dry, low elevation sites prevented conversion to cheatgrass-dominated systems, 3) drill seeded sites had fewer fires and increased in fire frequency more slowly than aerial seeded sites, 4) the on-the-ground conditions that led to the decision to aerially seeding after a fire led to more frequent and numerous fires.
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After a catastrophic wildfire, quick action must be taken to minimize social, environmental, and economic devastation. Responsive action requires navigating a complex maze of diverse landowners, community organizations, and numerous local and federal requirements.
Given enough time, forests eventually heal from wildfire. But that healing process can take decades, or even centuries. They simply won’t heal quickly without human intervention. Timely rehabilitation efforts reduce environmental impacts of fire, and can have a positive impact on the community’s social and economic situation in the months and years after the fire. Perhaps most importantly, quick and effective rehabilitation efforts improve public health and safety.
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This study approach revealed interactive, ecological relationships such as novel soil-surface effects on first year establishment of sagebrush across the burned landscape, and identified ‘‘hot spots’’ for recovery. The approach could be expanded across sites and years to provide the information needed to explain past seeding successes or failures, and in designing treatments at the landscape scale.
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Evidence from this analysis shows significant increases in nutrient flux (different forms of nitrogen and phosphorus), major-ion flux and metal concentrations are the most common changes in stream water quality within the first 5 years after fire. Dissolved constituents of ions and metals tended to decrease in concentration 5 years after fire whereas particulate matter concentration continued to increase. Assembling this unique and extensive dataset provided the opportunity to determine the most common post-fire water-quality changes in the large and diverse Western USA. Results from this study could inform studies in other parts of the world, will help parameterise and validate post-fire water-quality models, and assist communities affected by wildfire to anticipate changes to their water quality.