Proactive fuels management for old growth conservation in the Lake Tahoe Basin

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Proactive fuels management for old growth conservation in the Lake Tahoe Basin

Researchers at the University of California Davis and University of Nevada Reno modeled the outcomes of four fuels management scenarios followed by a simulated wildfire at Emerald Point in the Lake Tahoe Basin (LTB), an iconic MOG stand experiencing these vulnerabilities. The study found that a treatment involving thinning to within the forest’s historical “Natural Range of Variation” (NRV) followed by a fall broadcast burn was most effective in reducing projected large-tree mortality, maintaining stand basal area, and retaining post-wildfire live tree carbon. Researchers also discuss potential management co-benefits of treatments, such as reduced competition-driven tree mortality, increased understory biodiversity, raptor habitat conservation, and reduced air quality impacts.

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Reduced fire severity in fuel-treated forests at the Wildland-Urban Interface during the Caldor Fire (2021)

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Reduced fire severity in fuel-treated forests at the Wildland-Urban Interface during the Caldor Fire (2021)

This study assessed tree and stand characteristics and metrics of fire severity in areas within the footprint of the Caldor Fire that had experienced fuel reduction by the Forest Service between the early 2000s and 2019. Treatments were varied, and included hand-thinning and piling (HTP) followed by pile-burning, HTP where the piles were still onsite, and areas where treatment involved two rounds of “cut to length” tree-felling (DBH < 76.2 cm) followed by mastication and surface fuel redistribution to stay below a threshold of 15 cm depth (CPCM). Pre- and post-treatment fuel loadings, stand densities, and basal areas were calculated by combining field data, allometric modeling methods (Forest Vegetation Simulator), and photo series. Each of these metrics was significantly lower in treated stands.

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Wildfire Risk Perception and Communication in Disadvantaged Communities: Eastern Coachella Valley, Southern California

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Wildfire Risk Perception and Communication in Disadvantaged Communities: Eastern Coachella Valley, Southern California

Disadvantaged, geographically isolated communities in Eastern Coachella Valley (ECV) face recurrent wildfire threats and persistent barriers to preparedness including language challenges and limited government support. From February to April 2023, researchers surveyed 115 residents in four unincorporated ECV communities with recent wildfire experience. Nearly all respondents identified as Hispanic/Latino; 60% reported annual household incomes under $25,000. The study analyzed the associations between sociodemographic predictors and communication preferences.

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Hotter and drier fire seasons increase risk of severe wildfires in western US forests

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Hotter and drier fire seasons increase risk of severe wildfires in western US forests

Wildfire activity has been increasing across western US forests, impacting public health, infrastructure, water quality, and the economy. While total annual area burned is often used to track wildfire trends, high-severity fire (fire that kills all or most trees) can have longer lasting impacts on forests and communities and may be a more meaningful measure. Historically, many western US forests experienced frequent, low-severity fires, which promoted resistance to drought, insect outbreaks, and future wildfires. In contrast, high-severity fires in these forest types can lead to forest loss and have negative impacts on post-fire recovery. Understanding trends in high-severity fire is therefore crucial to understanding wildfire impacts on forests and the ecosystem services they provide. Although climate is a key driver of fire behavior, no studies to date have projected how much land could burn at high severity under future climate conditions. This study asks: how is high-severity wildfire changing under a warming climate in the western US, and what might the future look like?

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Carbon dynamics in Sierra Nevada wildfire use areas

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Carbon dynamics in Sierra Nevada wildfire use areas

Actively using wildfires to restore dry, frequent fire adapted forests in the western U.S. is an important management tool to meaningfully increase the scale of forest restoration and fuel reduction treatments. Using lightning-ignited wildfires to meet forest management objectives (also termed managed wildfire, wildfire for resource benefits, or Prescribed Natural Fire) has been particularly successful in Yosemite National Park, which has implemented a wildfire use policy since 1972. In a well-studied, remote basin in the southern part of the Park—Illilouette Creek Basin—reintroducing fire has been overwhelmingly positive (i.e., reduced fuel loads, reduced future fire spread and severity, increased land cover diversity, and increased water yield). Here, we add to this body of knowledge by investigating the impacts of wildfires on carbon stocks in two basins in the Sierra Nevada (Illilouette Creek basin in Yosemite and San Joaquin basin in the Ansel Adams Wilderness), compared to a nearby basin that has remained largely unburned (Badger basin in Yosemite).

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Opportunities to leverage beneficial areas of even undesirable wildfires

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Opportunities to leverage beneficial areas of even undesirable wildfires

Successive catastrophic wildfire seasons in western North America have escalated the urgency around reducing fire risk to communities and ecosystems. In historically frequent-fire forests, government agencies are committing significant resources to fuel reduction treatments that can reduce the probability of high severity wildfire. However, even catastrophic fires with large areas of high severity can still have substantial area of lower severity fire that may be improving forest conditions locally, acting as “treatments.” Understanding how these areas of beneficial fire compare and interact with active management can help inform treatment priorities and opportunities. As a test case, we explored trends in the yellow pine and mixed conifer forests (YPMC) in the Sierra Nevada of California over a 22-year period (2001-2022).

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Untrammeling the wilderness: restoring natural conditions through the return of fire

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Untrammeling the wilderness: restoring natural conditions through the return of fire

Within many designated wilderness areas, the intentional exclusion of fire has clearly altered ecological processes and thus constitutes a fundamental and ubiquitous act of trammeling. Through a framework that recognizes four orders of trammeling, the authors demonstrate the substantial, long-term, and negative effects of fire exclusion on the natural conditions of fire-adapted wilderness ecosystems. In order to untrammel more than a century of fire exclusion, the implementation of active programs of intentional burning may be necessary across some wilderness landscapes.

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Realignment of federal environmental policies to recognize fire’s role

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Realignment of federal environmental policies to recognize fire’s role

This article highlights the barriers that federal environmental statutes create for reintroducing and maintaining beneficial fire in fire-adapted and fire-dependent ecosystems, proposing specific policy reforms to support the use of beneficial fire on these landscapes.

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Fuel Management Approaches in Desert Wetlands

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Fuel Management Approaches in Desert Wetlands

In the Mojave Desert wetlands of Las Vegas, Nevada, a two-year study across 24 sites evaluated the outcomes of different management strategies for hazardous fuel reduction of the invasive common reed (Phragmites australis) and increasing native plant diversity. The study suggests that coupling active revegetation of native species with maintenance management activities to keep reed cover low could be a next research step in identifying long-term strategies for converting reed monocultures to more diverse native, less-fire-prone communities in desert wetlands.

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Prescribed Burn Windows Under Future Climatic Conditions

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Prescribed Burn Windows Under Future Climatic Conditions

Here, the authors review two studies that have assessed seasonality and duration of burn windows: A California-focused study on trends in historic burn windows (Baijnath-Rodino et al. 2022) and a Western US-focused study on recent trends and potential future changes (Swain et al. 2023). This brief will focus on the California-specific finding from Swain et al. (2023).

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Ecological Silviculture for Sierra Nevada Mixed Conifer Forests

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Ecological Silviculture for Sierra Nevada Mixed Conifer Forests

This brief discusses adjustments to current silvicultural systems in Sierra Nevada mixed conifer forests to align more closely with historical disturbance regimes, emphasizing ecological silviculture approaches like prescribed fire, mechanical treatments, and gap-based harvesting to enhance forest resilience and restoration.

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Using prescribed fires in young forests: A pyrosilvicultural approach

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Using prescribed fires in young forests: A pyrosilvicultural approach

This paper asserts that prescribed fire will be a key tool in the development of new approaches to reintroduce structural complexity in young forests and enable them to persist through future wildfires.

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The efficacy of Red Flag Warnings in mitigating human-caused wildfires

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The efficacy of Red Flag Warnings in mitigating human-caused wildfires

In our efforts to predict fire danger, we coupled CAL FIRE (California Department of Forestry and Fire Protection) FRAP (Fire and Resource Assessment Program) fire data with hourly climate data from four stations, and with regional indices of SAW wind speed, and with seasonal drought data from the Palmer Drought Severity Index. We found that different tools work better for SAW fires versus non-SAW fires.

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Climate and weather drivers in southern California Santa Ana Wind and non-Santa Wind fires

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Climate and weather drivers in southern California Santa Ana Wind and non-Santa Wind fires

In our efforts to predict fire danger, we coupled CAL FIRE (California Department of Forestry and Fire Protection) FRAP (Fire and Resource Assessment Program) fire data with hourly climate data from four stations, and with regional indices of SAW wind speed, and with seasonal drought data from the Palmer Drought Severity Index. We found that different tools work better for SAW fires versus non-SAW fires.

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Human and climatic influences on wildfires ignited by recreational activities in national forests in Washington, Oregon, and California

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Human and climatic influences on wildfires ignited by recreational activities in national forests in Washington, Oregon, and California

Fire is strongly linked to outdoor recreation in the United States. Recreational uses of fires, whether in designated campgrounds or the backcountry, include warmth, cooking, and fostering a comfortable atmosphere. However, through inattention, negligence, or bad luck, recreational fires sometimes ignite wildfires. This paper evaluates whether the density of wildfire ignited by recreation or ceremony on U.S. Forest Service lands, and the size of such wildfires, is influenced by proximity to designated campgrounds, visitor density, previous and current drought conditions, and the type of vegetation surrounding the ignition point.

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Thinning + burning treatments effectively reduce fire severity

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Thinning + burning treatments effectively reduce fire severity

Although fuels treatments are generally shown to be effective at reducing fire severity, there is widespread interest in monitoring that efficacy as the climate continues to warm and the incidence of extreme fire weather increases. This paper compared basal area mortality across adjacent treated and untreated sites in the 2021 Dixie Fire of California’s Sierra Nevada.

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Using historical aerial imagery to assess non-conifer vegetation type change under fire exclusion

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Using historical aerial imagery to assess non-conifer vegetation type change under fire exclusion

Although vegetation types other than conifer forests make up the majority of burned area in California wildfires, relatively few studies quantify the drivers and patterns of vegetation change in these ecosystems. The impacts of fire exclusion on non-conifer systems remain poorly understood, and the relative influence of fuels compared to factors like climate change or type conversion on fire behavior is largely unknown. To address this knowledge gap, the authors investigated large-scale vegetation change as a possible driver of current trends in fire behavior within mixed-hardwood and shrub-dominated ecosystems in central and coastal Northern California.

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Assessing giant sequoia mortality and regeneration following high-severity wildfire

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Assessing giant sequoia mortality and regeneration following high-severity wildfire

Giant sequoia (Sequoiadendron giganteum) regeneration is reliant on local surface fires, where episodic pulses of heat desiccate and open their cones, releasing seed onto bare mineral soil. Historically, these fires were characterized as ‘mixed severity’, composed of a large matrix that burned at low or moderate severity interspersed with small forest gaps created by local high severity fire. While sequoia regeneration can flourish within these small, high severity gaps,recent ‘megafires’ have produced unprecedentedly large patches of high severity, where the majority of sequoias as killed. This research aims to help resource managers determine whether and where to replant giant sequoia after high severity wildfire.

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Where are the Sierra Nevada’s large trees and can they persist?

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Where are the Sierra Nevada’s large trees and can they persist?

Identification and conservation of mature and old-growth forests has become a federal government priority.  In California’s Sierra Nevada’s most of the remaining large trees are concentrated on Forest Service and National Park Service lands. We used airborne lidar data to census large (≥30” diameter at breast height (DBH)) and very large (≥40”) trees across three large Sierra landscapes. We found that large trees are either locally absent to rare or are aggregated in stands with 8-20 large trees per acre.

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Using Stand Density Index (SDI) as a stocking guide in frequent fire forests

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Using Stand Density Index (SDI) as a stocking guide in frequent fire forests

Quantification of competition levels in forest stands benefits assessments of stand health, vulnerability to stressors, and prediction of future stand dynamics. Because different forests have different carrying capacities that can be maintained given differences in site productivities, it is important to consider stocking in terms that are relative to these maximum levels. Stand Density Index (SDI) is a common metric of competition in temperate forests of Western North America, originating in 1933 and gaining widespread use within the field of forestry throughout the 20th century. The authors of this study synthesized the large body of published literature on SDI since its introduction in 1933.

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