Fire Regimes

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How climate change and fire exclusion drive wildfire regimes at actionable scales

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Extreme wildfires are increasing in frequency globally, prompting new efforts to mitigate risk. The ecological appropriateness of risk mitigation strategies, however, depends on what factors are driving these increases. While regional syntheses attribute increases in fire activity to both climate change and fuel accumulation through fire exclusion, they have not disaggregated causal drivers at scales where land management is implemented. Recent advances in fire regime modeling can help us understand which drivers dominate at management-relevant scales. We conducted fire regime simulations using historical climate and fire exclusion scenarios across two watersheds in the Inland Northwestern U.S., which occur at different positions along an aridity continuum. In one watershed, climate change was the key driver increasing burn probability and the frequency of large fires; in the other, fire exclusion dominated in some locations. We also demonstrate that some areas become more fuel-limited as fire-season aridity increases due to climate change. Thus, even within watersheds, fuel management must be spatially and temporally explicit to optimize effectiveness. To guide management, we show that spatial estimates of soil aridity (or temporally averaged soil moisture) can provide a relatively simple, first-order indicator of where in a watershed fire regime is climate vs. fuel-limited and where fire regimes are most vulnerable to change.

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Weekly CA fire science seminar series

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This online seminar series will cover the breadth of wildland fire research relevant to California and introduce researchers to new topics and research groups across the state. Topics will include fire weather, wildfire risk, fire ecology, remote sensing, emissions, fire dynamics, fire modeling and public health. Featuring many early-career researchers, this series is aimed at a highly interdisciplinary academic audience but is open to anyone interested in these topics.

View an up-to-date schedule here:

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The effects of prescribed fire on wildfire regimes and impacts

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Prescribed fire can result in significant benefits to ecosystems and society. Examples include improved wildlife habitat, enhanced biodiversity, reduced threat of destructive wildfire, and enhanced ecosystem resilience. Prescribed fire can also come with costs, such as reduced air quality and impacts to fire sensitive species. To plan for appropriate use of prescribed fire, managers need information on the tradeoffs between prescribed fire and wildfire regimes. In this study, we argue that information on tradeoffs should be presented at spatial and temporal scales commensurate with the scales at which these processes occur and that simulation modeling exercises should include some realistic measure of wildfire probability. To that end, we synthesized available scientific literature on relationships between prescribed fire and wildfire regimes, and their associated ecological and societal effects, focusing specifically on simulation modeling studies that consider wildfire probability and empirical and modeling studies that consider prescribed fire and wildfire regimes at spatial and temporal scales beyond individual events.

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Patterns and trends in wildfire activity in the US from 1984-2015

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This study shows that simultaneous wildfire is at least as correlated with preparedness levels as other burned area measures and identify changes in simultaneous wildfire occurrence within the western and southern United States. Seasonal variation and spatial autocorrelation in simultaneous wildfire occurrence provide evidence of coupling of wildfire activity in portions of the western United States. Best-approximating models of simultaneity suggest that high levels of simultaneous wildfire often coincided with low fuel moisture and high levels of lightning occurrence. Model uncertainty was high in some contexts but, with only a few exceptions, there was strong evidence that the best model should include both a dryness and lightning indicator.

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Invasive Annual Grass Workshop

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Invasive annual grasses threaten millions of acres of sagebrush rangelands across the west. This two day workshop hosted by the Harney County Wildfire Collaborative and Oregon SageCon Partnership will explore the barriers and opportunities for addressing invasive annual grasses in Oregon and beyond the state. In this workshop some of the most pressing issues related to invasive annual grass management will be discussed, including the connection between invasive annual grasses and wildfire and what can be done to better address this threat.

VIRTUAL Workshop Dates & Agenda
Monday, December 14, 12:30-4:30pm: Defend the Core—Keeping the Good, Good

  • Hard truths of invasive annual grasses
  • Stopping the Spread
  • Supersizing Suppression Success
  • Reducing Wildfire Risk
  • Ratcheting Up Resiliency

Tuesday, December 15, 8:30am-12:30pm: Grow the Core—Restoring At-Risk and Converted Lands

  • Managing Invasive Annual Grasses
  • Innovative Restoration
  • Prioritizing Limited Resources & Sustaining Long-term Investment
  • Where Do We Go From Here
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Restoration in a fire forest: The benefits of burning

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Wildfire has historically played an important role in the health and structure of Oregon’s dry forests. Prescribed fire is a valuable tool used to restore forest health, increase firefighter safety, and better protect nearby human resources in these fire-adapted landscapes.

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Misconceptions and benefits of fire

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The most common misconception of wildfire is that all fire is bad. But there are important benefits that smaller and more frequent fires offer to the environment. Matt Jolly, an ecologist at the U.S. Forest Service Rocky Mountain Research Station, talks about the natural and important role of fire in maintaining a healthy ecosystem.

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Re-introducing fire in sagebrush steppe experiencing decreased fire frequency: Does burning promote spatial and temporal heterogeneity?

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Fire frequency has decreased in many shrub-steppe communities. Re-introducing fire may be needed to increase spatial and temporal variability in vegetation, but is often hindered by concerns of undesired vegetation shifts. These concerns arise, in part, because long-term effects of fire re-introduction in these communities after prolonged fire exclusion and other departures from historical conditions are unknown. To better understand the effects of re-introducing fire, we evaluated plant community response to re-introducing fire for 12 years post fire in six mountain big sagebrush communities. Herbaceous biomass production was 1.7-fold greater in burned compared with unburned areas at the conclusion of the study. Exotic annual grasses appeared to be problematic in the first 8 years post fire, but became inconsequential (~1% cover) by the end of the study. Re-introducing fire promoted other shrubs (excluding sagebrush) that were probably inhibited by competition from sagebrush. Sagebrush cover and density remained low in burned areas for the duration of the study, because of limited recruitment in the years immediately post fire and competition from herbaceous vegetation. Re-introducing fire appears to increase temporal and spatial heterogeneity in shrub-steppe communities experiencing prolonged fire exclusion and, therefore, may be needed to maintain a diversity of plant communities.

Prescribed fire

Megafires: Climate change or land management?

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In the Western U.S., the 2020 fire season is setting new records in terms of geographic scale, fire intensity, and rates of spread. Tens of millions of people are currently being forced to breathe beneath a dense layer of smoke, as others have lost their lives and property.

With each new record-setting fire, the same question comes up again and again: is this due to climate change, or is this due to forest mismanagement? After dueling appearances on Monday, this question now appears to be a matter of debate in the Presidential campaign.

The climate change vs. management question ignores nuance that is crucial for finding scientific answers and policy solutions. The factors influencing wildfire behavior are complex, and the dominant drivers vary between different locations and events. Below are five key things to know about the causes of the current wildfire problem. Understanding them can help us navigate the question of what is driving increased fire activity and what can be done to reduce such large fires in the future.

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Historical range of variability (HRV): Uses and various approaches

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Description: Range of Variability (ROV) concepts – including Natural (NRV), Historic (HRV), Current (CRV), and Future (FRV) – are frequently used by the US Forest Service to help define land management goals. This webinar provides an introduction to ROV terminology and examples of how the Malheur, Umatilla, and Wallowa-Whitman National Forests in the Blue Mountains have applied ROV concepts during project planning when addressing key requirements of the Eastside Screens. The discussion includes overviews of tools commonly used to conduct ROV analyses.

Presenter: Nathan Poage, Forest Service Ecologist,

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