Bark Beetles and High-Severity Fires in Rocky Mountain Subalpine Forests

Kulakowski, Dominik; Veblen, Thomas T.

doi:10.1016/b978-0-12-802749-3.00006-2

Cited by 6 publications

(8 citation statements)

References 88 publications

(104 reference statements)

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“…How quickly CBD decreases following outbreaks necessarily hinges on the synchrony of beetle attack and tree death within a stand, as well as site conditions (Hicke et al. , Kulakowski and Veblen ). For instance, after substantial reduction of stand‐scale foliar moisture content (FMC), stand‐level CBD would be most likely to remain unchanged following outbreaks if 100% of trees in a stand were killed during the initial year of the outbreak and if site moisture, temperature, and wind conditions promoted retention of dead needles.…”

Section: Discussionmentioning

confidence: 99%

“…In contrast, empirical studies have generally found that wildfire hazard, occurrence, and severity do not substantially increase following MPB outbreaks, though results have not been consistent (e.g., reviewed in Hicke et al. , Kulakowski and Veblen ). Ongoing outbreaks of MPB in Colorado, USA, had no detectable effect on the extent or severity of a fire during a drought in 2002, even though recently killed trees were in the critical red phase (Kulakowski and Veblen ).…”

Section: Introductionmentioning

confidence: 95%

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Relative importance of climate and mountain pine beetle outbreaks on the occurrence of large wildfires in the westernUSA

Mietkiewicz

Kulakowski

2016

Ecological Applications

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Extensive outbreaks of bark beetles have killed trees across millions of hectares of forests and woodlands in western North America. These outbreaks have led to spirited scientific, public, and policy debates about consequential increases in fire risk, especially in the wildland-urban interface (WUI), where homes and communities are at particular risk from wildfires. At the same time, large wildfires have become more frequent across this region. Widespread expectations that outbreaks increase extent, severity, and/or frequency of wildfires are based partly on visible and dramatic changes in foliar moisture content and other fuel properties following outbreaks, as well as associated modeling projections. A competing explanation is that increasing wildfires are driven primarily by climatic extremes, which are becoming more common with climate change. However, the relative importance of bark beetle outbreaks vs. climate on fire occurrence has not been empirically examined across very large areas and remains poorly understood. The most extensive outbreaks of tree-killing insects across the western United States have been of mountain pine beetle (MPB; Dendroctonus ponderosae), which have killed trees over >650,000 km , mostly in forests dominated by lodgepole pine (Pinus contorta). We show that outbreaks of MPB in lodgepole pine forests of the western United States have been less important than climatic variability for the occurrence of large fires over the past 29 years. In lodgepole pine forests in general, as well as those in the WUI, occurrence of large fires was determined primarily by current and antecedent high temperatures and low precipitation but was unaffected by preceding outbreaks. Trends of increasing co-occurrence of wildfires and outbreaks are due to a common climatic driver rather than interactions between these disturbances. Reducing wildfire risk hinges on addressing the underlying climatic drivers rather than treating beetle-affected forests.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 95%

Relative importance of climate and mountain pine beetle outbreaks on the occurrence of large wildfires in the westernUSA

Mietkiewicz

Kulakowski

2016

Ecological Applications

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“…, Simard et al. , Kulakowski and Veblen ). In extreme cases, compounded disturbances may push a community to an alternate stable state (Paine et al.…”

Section: Introductionmentioning

confidence: 98%

“…Current understanding of regeneration following multiple disturbances suggests that an interacting effect may emerge in two ways-through the effect of a first disturbance on the occurrence, intensity, severity, or other attributes of a subsequent disturbance, or through a compounded effect that alters the nature of post-disturbance development (Donato et al 2009a, Simard et al 2011, Kulakowski and Veblen 2015. In extreme cases, compounded disturbances may push a community to an alternate stable state (Paine et al 1998).…”

Section: Introductionmentioning

confidence: 99%

Is initial post‐disturbance regeneration indicative of longer‐term trajectories?

et al. 2017

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Abstract. The ability to estimate and model future vegetation dynamics is a central focus of contemporary ecology and is essential for understanding future ecological trajectories. It is therefore critical to understand when the influence of initial post-disturbance regeneration versus stochastic processes dominates long-term post-disturbance ecological processes. Often, conclusions about post-disturbance dynamics are based upon initial regeneration in the years immediately after disturbances. However, the degree to which initial post-disturbance regeneration indicates longer-term trends is likely to be contingent on the types, intensities, and combinations of disturbances, as well as pre-disturbance ecosystem structure and composition. Our relatively limited understanding of why initial post-disturbance regeneration is sometimes a poor predictor of future ecosystem trajectories represents a critical gap in post-disturbance ecological forecasting. We studied the composition and density of regeneration of tree species following wind blowdown in 1997, wildfire in 2002, and compounded disturbances by blowdown and wildfire in subalpine forests of Colorado. We examined regeneration of Picea engelmannii, Abies lasiocarpa, Pinus contorta, and Populus tremuloides in 180 permanent plots across 12 sites (classified by pre-disturbance age and composition) in 2003, 2010, and 2015. At sites that were blown down but not burned, regeneration was dense and dominated by Picea and Abies. At these sites, regeneration observed from 2003 to 2005 (hereafter initial regeneration) was also highly predictive of regeneration 5-10 yr later. In contrast, at sites that were burned and sites that were blown down and burned, regeneration was less dense and dominated by a mix of species. At these sites, initial regeneration was a poor predictor of longer-term trends as species dominance and overall density fluctuated over the 13-yr period. These findings call into question our ability to confidently predict ecosystem trajectories based upon observations made in the years immediately after large, severe disturbances such as wildfires and compounded disturbances. As compounded disturbances become more common under climatically driven changes in disturbance regimes, post-disturbance ecosystem trajectories may become increasingly stochastic and unpredictable.

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“…Notably, numerous studies have found high levels of native plant and animal richness and abundance in large fires of mixed severity that produce CESF patches in severely burned areas, see [3,[24][25][26][27][28][29][30][31]70,74,75]. Such fires facilitate high levels of beta diversity at landscape scales, providing a broad suite of habitat for both fire-seeking and fire-avoiding species [25], including many early seral birds that have been declining due to a lack of "diverse early seral habitat" [76].…”

Section: Discussionmentioning

confidence: 99%

Are Wildland Fires Increasing Large Patches of Complex Early Seral Forest Habitat?

DellaSala

Hanson

2019

Diversity

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High-severity fire creates patches of complex early seral forest (CESF) in mixed-severity fire complexes of the western USA. Some managers and researchers have expressed concerns that large high-severity patches are increasing and could adversely impact old forest extent or lead to type conversions. We used GIS databases for vegetation and fire severity to investigate trends in large (>400 ha) CESF patches in frequent-fire forests of the western USA, analyzing four equal time periods from 1984 to 2015. We detected a significant increase in the total area of large patches relative to the first time period only (1984–1991), but no significant upward trend since the early 1990s. There was no significant trend in the size of large CESF patches between 1984 and 2015. Fire rotation intervals for large CESF patches ranged from ~12 centuries to over 4000 years, depending on the region. Large CESF patches were highly heterogeneous, internally creating ample opportunities for fire-mediated biodiversity. Interior patch areas far removed from the nearest low/moderate-severity edges comprised a minor portion of high-severity patches but may be ecologically important in creating pockets of open forest. There was ample historical evidence of large CESF patches but no evidence of increases that might indicate a current risk of ecosystem-type shifts.

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Bark Beetles and High-Severity Fires in Rocky Mountain Subalpine Forests

Cited by 6 publications

References 88 publications

Relative importance of climate and mountain pine beetle outbreaks on the occurrence of large wildfires in the westernUSA

Relative importance of climate and mountain pine beetle outbreaks on the occurrence of large wildfires in the westernUSA

Is initial post‐disturbance regeneration indicative of longer‐term trajectories?

Are Wildland Fires Increasing Large Patches of Complex Early Seral Forest Habitat?

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