Drivers of Fuels, Flammability, and Fire Behavior in Young, Post-fire Lodgepole Pine Forests

Drivers of Fuels, Flammability, and Fire Behavior in Young, Post-fire Lodgepole Pine Forests
Author: Kellen N. Nelson
Publisher:
Total Pages: 123
Release: 2017
Genre: Climatic changes
ISBN: 9780355093513

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Fire and bark beetles have affected vast areas of forest over the past several decades raising concern about the risk of subsequent burning. Little is known about how fuel loads and fire behavior vary shortly after burning, nor how forest flammability might differ between stands recovering from fire and bark beetles. To address this, we investigated the variation and drivers of fuel characteristics (Chapter 2) and fire behavior (Chapter 3) in 24-year-old post-fire lodgepole pine (Pinus contorta var. latifolia) stands that regenerated after the 1988 Yellowstone Fires. To assess differences in flammability between disturbance types (Chapter 4), we intensively sampled meteorological conditions and fuel moisture content in adjacent burned and bark beetle-affected forest sites. Both sites were approximately 24 years since disturbance. Our results indicate that fuel characteristics varied tremendously across the post-1988 Yellowstone landscape and were sufficient to support fire in all stands. Total surface-fuel loads in post-disturbance forests were similar or greater than those reported in mature lodgepole pine stands; however, 88% of fuel was in the 1000-hr fuel class, and litter, 1-hr, and 10-hr surface fuel loads were lower than values reported for mature lodgepole pine forests. Pre-fire successional stage was the best predictor of 100-hr and 1000-hr fuel and strongly influenced the size and proportion of sound and rotten logs, where post-fire stand structure was the best predictor of litter, 1-hr, and 10-hr fuels. Available canopy fuel loads and canopy bulk density met or exceeded loads observed in mature lodgepole pine forests, exhibited a strong positive relationship with post-fire lodgepole pine density, and were the primary drivers of crown fire behavior. Meteorological conditions in post-fire sites exhibited symptoms of earlier snowmelt, greater evapotranspiration, and greater drought stress than post-bark beetle sites, and live fuel moisture content mimicked these differences as post-fire sites broke dormancy earlier and experienced longer, more severe drought conditions than post-bark beetle sites. Dead fuel moisture content was similar in burned and bark beetle affected sites in July, but had a greater response to heavy August precipitation that resulted in higher dead fuel moisture content on the post-burn sites. In sum, our data suggest that 76% of the young post-fire lodgepole pine forests have 1000-hr fuel loads that exceed levels associated with high-severity surface fire, and 63% exceed canopy bulk densities associated with spreading crown fire. Fire simulation modeling predicted active crown fire in 90% of stands at wind speeds >20 km hr−1, regardless of fuel moisture condition. We conclude that 24-year old lodgepole pine forests can readily support fire intervals shorter than those observed historically in Yellowstone National Park, and that dead fuel moisture content appears more dynamic while foliar fuel moisture content might be less dynamic on post-fire sites than post-bark beetle sites. Overall, the potential for crown fire is high across the post-1988 Yellowstone landscape, and post-fire sites appear to be more flammable than post-bark beetle sites during dry periods. Given a less developed canopy seed bank and a high potential for crown fire, young post-fire lodgepole pine forests are likely to have lower reproductive potential than comparable mature forests. Progressive reductions in tree recruitment after short-interval fires may lead to self-limiting dynamics where lack of fuels limit continued short-interval burning.

Effects of Fire on Fuels

Effects of Fire on Fuels
Author: Robert Edward Martin
Publisher:
Total Pages: 72
Release: 1979
Genre: Biomass energy
ISBN:

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Fire managers field guide

Fire managers field guide
Author:
Publisher:
Total Pages: 72
Release: 2010
Genre: Forests and forestry
ISBN:

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FUELBED-EAST

FUELBED-EAST
Author: David L. Radloff
Publisher:
Total Pages: 20
Release: 1984
Genre: Forest fire forecasting
ISBN:

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Landscape Variation in Tree Regeneration and Snag Fall Drive Fuel Loads in 24-year Old Post-fire Lodgepole Pine Forests

Landscape Variation in Tree Regeneration and Snag Fall Drive Fuel Loads in 24-year Old Post-fire Lodgepole Pine Forests
Author: Kellen N. Nelson
Publisher:
Total Pages:
Release: 2016
Genre: Lodgepole pine
ISBN:

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Escalating wildfire in subalpine forests with stand-replacing fire regimes is increasing the extent of early-seral forests throughout the western USA. Post-fire succession generates the fuel for future fires, but little is known about fuel loads and their variability in young post-fire stands. We sampled fuel profiles in 24-year- old post-fire lodgepole pine (Pinus contorta var. latifolia) stands (n = 82) that regenerated from the 1988 Yellowstone Fires to answer three questions. (1) How do canopy and surface fuel loads vary within and among young lodgepole pine stands? (2) How do canopy and surface fuels vary with pre-and post-fire lodgepole pine stand structure and environmental conditions? (3) How have surface fuels changed between eight and 24 years post-fire? Fuel complexes varied tremendously across the landscape despite having regenerated from the same fires. Available canopy fuel loads and canopy bulk density averaged 8.5 Mg/ha (range 0.0?46.6) and 0.24 kg/m3 (range: 0.0?2.3), respectively, meeting or exceeding levels in mature lodgepole pine forests. Total surface-fuel loads averaged 123 Mg/ha (range: 43?207), and 88% was in the 1,000-h fuel class. Litter, 1-h, and 10-h surface fuel loads were lower than reported for mature lodgepole pine forests, and 1,000-h fuel loads were similar or greater. Among-plot variation was greater in canopy fuels than surface fuels, and within-plot variation was greater than among-plot variation for nearlyall fuels. Post-fire lodgepole pine density was the strongest positive predictor of canopy and fine surface fuel loads. Pre-fire successional stage was the best predictor of 100-h and 1,000-h fuel loads in the post-fire stands and strongly influenced the size and proportion of sound logs (greater when late successional stands had burned) and rotten logs (greater when early successional stands had burned). Our data suggest that 76% of the young post-fire lodgepole pine forests have 1,000-h fuel loads that exceed levels associated with high-severity surface fire potential, and 63% exceed levels associated with active crown fire potential. Fire rotations in Yellowstone National Park are predicted to shorten to a few decades and this prediction cannot be ruled out by a lack of fuels to carry repeated fires.