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

Brodie, Emily G.; Knapp, Eric E.; Latimer, Andrew M.; Safford, Hugh D.; Vossmer, Marissa; Bisbing, Sarah M.

doi:10.1016/j.foreco.2023.121011

Cited by 3 publications

(2 citation statements)

References 47 publications

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“…In the 1920s, commercial logging operations at GAMA prioritized large ponderosa pine for extraction (Ritchie 2005). At this site, as in others throughout California and the western USA, fire exclusion and the removal of overstory pines favored the more shade tolerant and fire-sensitive species, thus shifting the stands away from pine (Brodie et al 2023) and resulting in a predominantly two species mix of white fir and ponderosa pine (Ritchie 2020). Fire exclusion also contributed to increased surface fuel loading and stand density (Agee & Skinner 2005;Knapp et al 2013).…”

Section: Locationmentioning

confidence: 91%

Forest thinning and prescribed burning treatments reduce wildfire severity and buffer the impacts of severe fire weather

Brodie,

Knapp,

Brooks

et al. 2024

fire ecol

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Background The capacity of forest fuel treatments to moderate the behavior and severity of subsequent wildfires depends on weather and fuel conditions at the time of burning. However, in-depth evaluations of how treatments perform are limited because encounters between wildfires and areas with extensive pre-fire data are rare. Here, we took advantage of a 1200-ha randomized and replicated experiment that burned almost entirely in a subsequent wildfire under a wide range of weather conditions. We compared the impacts of four fuel treatments on fire severity, including two thin-only, a thin-burn, a burn-only, and an untreated control. We evaluated four fire severity metrics—tree mortality, average bole char height, percent crown volume consumed (PCVC), and percent crown volume affected (PCVA)—and leveraged data from pre-fire surface and canopy fuels to better understand the mechanisms driving differences in wildfire severity among treatments and how they changed with fire weather. Results We found strong mitigating effects of treatments on fire behavior and tree mortality, despite 20 years having elapsed since mechanical thinning and 10 years since the second entry of prescribed fire. The thin-burn treatment resulted in the lowest fire severity across all four metrics and the untreated control the highest. All four fire severity metrics were positively associated with pre-fire canopy and surface fuel loads, with the exception that PCVC (a fire severity metric related to crown fire behavior) was not associated with surface fuel load. The fire weather conditions under which fuel treatment was most effective varied among fire severity metrics. Fuel treatment benefit was maximized at intermediate burning index values for tree mortality, intermediate to high burning index values for PCVA, and high burning index for bole char height and PCVC. Conclusions We conclude that reducing canopy bulk density via mechanical thinning treatments can help to limit crown fire behavior for 20 years or more. However, reducing surface fuels is necessary to limit scorching and the total crown impacts associated with tree mortality. Further, while fuel treatment effectiveness may decline under the most severe fire weather conditions for fire severity metrics associated with tree mortality, it is maximized under severe fire weather conditions for fire severity metrics associated with crown fire behavior (bole charring and torching). Our results provide strong evidence for the use of fuel treatments to mitigate fire behavior and resulting fire severity even under extreme fire weather conditions.

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Section: Locationmentioning

confidence: 91%

Forest thinning and prescribed burning treatments reduce wildfire severity and buffer the impacts of severe fire weather

Brodie,

Knapp,

Brooks

et al. 2024

fire ecol

Self Cite

View full text Add to dashboard Cite

show abstract

“…In the 1920's, commercial logging operations at GAMA prioritized large ponderosa pine for extraction (Ritchie, 2005). At this site, as in others throughout California and the western United States, re exclusion and the removal of overstory pines favored the more shade tolerant and re sensitive species, thus shifting the stands away from pine (Brodie et al, 2023) and resulting in a predominantly two species mix of white r and ponderosa pine at the study site (Ritchie, 2020). Fire exclusion also contributed to increased surface fuel loading and stand density ( Ritchie, 2005).…”

Section: Locationmentioning

confidence: 95%

Forest thinning and prescribed burning treatments reduce wildfire severity and buffer the impacts of severe fire weather

Brodie,

Knapp,

Brooks

et al. 2023

Preprint

Self Cite

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Background: The capacity of forest fuel treatments to limit the behavior and severity of subsequent wildfires depends on weather and fuel conditions at the time of burning. We compared the impacts of five fuel treatments—including two thin-only, a thin-burn, a burn-only, and a control—on fire severity using a 1200 hectare randomized and replicated experiment that burned almost entirely in a subsequent wildfire. We evaluated four fire severity metrics (mortality, average bole char height, percent crown volume torched [PCVT], and percent crown volume affected [PCVA]) and leveraged pre-fire surface and canopy fuels data to better understand the mechanisms driving differences in wildfire severity among treatments and how they changed with fire weather. Results: We found strong mitigating effects of treatments on fire behavior and tree mortality, despite 20 years having elapsed since mechanical thinning and 10 years since the second entry of prescribed fire. The thin-burn treatment resulted in the lowest fire severity across all four metrics and the untreated control the highest. Prefire canopy and surface fuel loads were associated with all four fire severity metrics, with the exception that surface fuel loads were not associated with PCVT, a fire severity metric associated with crown fire behavior. The relationship between fuel treatment effectiveness and fire weather varied among fire severity metrics, with maximum fuel treatment benefit at intermediate burning index values for tree mortality, intermediate to high burning index values for PCVA, and high burning index for bole char height and PCVT. Conclusions: We conclude that reducing canopy bulk density via mechanical thinning treatments can help to limit crown fire behavior for 20 years or more. However, reducing surface fuels is necessary to limit scorching and the total crown impacts associated with tree mortality. Further, while fuel treatment effectiveness may decline at the most severe fire weather for some fire severity metrics (total crown impacts and mortality), it is maximized under severe fire weather conditions for others (bole charring and torching). Our results provide strong evidence for the use of fuel treatments to mitigate fire behavior and resulting fire severity even under extreme fire weather conditions.

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Ecological forestry treatments affect fine-scale attributes within large experimental units to influence tree growth, vigor, and mortality in ponderosa pine/white fir forests in California, U.S.

Looney,

Brodie,

Fettig

et al. 2024

Forest Ecology and Management

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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

Cited by 3 publications

References 47 publications

Forest thinning and prescribed burning treatments reduce wildfire severity and buffer the impacts of severe fire weather

Forest thinning and prescribed burning treatments reduce wildfire severity and buffer the impacts of severe fire weather

Forest thinning and prescribed burning treatments reduce wildfire severity and buffer the impacts of severe fire weather

Ecological forestry treatments affect fine-scale attributes within large experimental units to influence tree growth, vigor, and mortality in ponderosa pine/white fir forests in California, U.S.

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