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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Fire suppression biases fires to be more extreme

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Fire suppression biases fires to be more extreme

Decades of fire suppression have increased fuel loads and fire severity, leading to the “fire suppression paradox”—by suppressing fires we make fires harder to put out in the future. However, in this study, the authors show a separate impact of fire suppression that may cause even greater increases in average fire severity than climate change or fuel accumulation.

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Climate change is narrowing and shifting prescribed fire windows

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Climate change is narrowing and shifting prescribed fire windows

In this study, the authors used observed weather and climate data, as well as climate model simulations, to project shifts in the frequency and seasonality of burn windows in the Western United States. Real-world burn plans were used to calculate median upper and lower prescription values for weather, climate, and vegetation parameters. These upper and lower median values determined days that were suitable for prescribed fire (RxDay) at a given location, in both the past and in a warmer climate future.

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The century-long shadow of fire exclusion: Historical data reveal early and lasting effects of fire regime change on contemporary forest composition

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The century-long shadow of fire exclusion: Historical data reveal early and lasting effects of fire regime change on contemporary forest composition

This study explores the effects of historical logging on tree regeneration and successive effects on stand development under a history of fire exclusion. The authors leveraged a silvicultural experiment from the 1920s in the Sierra Nevada mixed-conifer forest of the Stanislaus-Tuolumne Experimental Forest to test if silvicultural objectives of increasing pine stocking rates were met. Combining historical (pre- and post-logging in 1928-1929) and contemporary tree regeneration data along with overstory and microsite conditions, they assessed the impact of logging on pine decline.

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Trends in prescribed fire weather windows from 2000 to 2022 in California

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Trends in prescribed fire weather windows from 2000 to 2022 in California

This study analyzed a 2-km hourly gridded weather dataset over a 23-year period to investigate the influence of climatological trends on prescribed fire weather windows. The authors explored how prescribed fire windows changed over this period for two California counties: Sonoma County near the coast and Plumas County in the Sierra Nevada, which contrast in land ownership types, vegetation, and climate. These counties represent diverse prescribed fire considerations in regions where recent catastrophic wildfire has drawn interest from land managers. Using burn prescriptions written by experienced local fire practitioners, the authors identified the degree of weather-driven change in prescribed fire opportunities for these two distinct areas within California.

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Degradation and restoration of Indigenous California black oak (Quercus kelloggii) stands in the northern Sierra Nevada

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Degradation and restoration of Indigenous California black oak (Quercus kelloggii) stands in the northern Sierra Nevada

This study summarizes Indigenous oral traditions, assesses current and historical forest structure, and measures fire effects of the 2021 Dixie Fire to understand the state of forests in the northern Sierra Nevada with cultural significance to the Mountain Maidu. Oral traditions of the Mountain Maidu cultural burning practices were passed down through generations and were incorporated into this work by one of the authors. The focal site of the study was the Plumas National Forest expanded on University of California, and data included Berkeley forest inventory plots, a California black oak census, and dendroecological fire history records. Regional forest conditions were assessed historically via a 1924 forest inventory, while current conditions were quantified through data from the Forest Inventory Analysis program.

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Forest restoration and fuels reduction work: Different pathways for achieving success in the Sierra Nevada

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Forest restoration and fuels reduction work: Different pathways for achieving success in the Sierra Nevada

This paper examines a 20-year forest restoration study in the northern Sierra Nevada looking at changes in forest structure and composition, fuel accumulation, modeled fire behavior, intertree competition, and economics resulting from four treatment regimes: multiple applications of prescribed fire (Fire), multiple mechanical restoration thinnings (Mech), multiple mechanical restoration thinnings followed by prescribed fire (Mech + Fire), and untreated controls

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Biogeomorphic Responses to Wildfire in Fluvial Ecosystems

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Biogeomorphic Responses to Wildfire in Fluvial Ecosystems

Biogeomorphic Responses to Wildfire in Fluvial Ecosystems draws together interdisciplinary studies and reviews that highlight key insights important to support heterogeneity, biodiversity, and resilience in fluvial ecosystems (Florsheim et al., 2024).

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Prescribed fire and mastication reduced bark-beetle-caused pine mortality

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Prescribed fire and mastication reduced bark-beetle-caused pine mortality

This study analyzes data from a mixed-severity fire in the northern range of coast redwood to create a model for predicting postfire response of four redwood community plants.Mastication, thinning, and prescribed fire can help shift fire-prone forests to a structure more resilient to fire and other disturbances. However, the ability to evaluate treatment effectiveness requires long-term monitoring of forest responses to disturbances and assessing changes in fuel loadings and structure. Researchers from Michigan State University and the USFS Fire Behavior Assessment Team remeasured a ponderosa pine forest 13 years after a combination of treatments were implemented: no treatment/control (C), mastication (M), mastication + burn (MB), and mastication + pull back of surface fuels + burn (MPB).

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Adaptive Strategies for Managing Bishop pine with Fire

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Adaptive Strategies for Managing Bishop pine with Fire

This study investigates Bishop pine's unique fire ecology, seed bank dynamics, and the impacts pine pitch canker infection has on stands.

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