Do tree and stand-level attributes determine susceptibility of spruce-fir forests to spruce beetle outbreaks in the early 21st century?

Hart, Sarah J.; Veblen, Thomas T.; Kulakowski, Dominik

doi:10.1016/j.foreco.2013.12.035

Cited by 43 publications

(61 citation statements)

References 32 publications

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“…Since the development of this study, there has been increased research, mostly retrospectively, on spruce beetle dynamics [18,32,40,63]. However, our study is unique for two reasons: (1) it tests a pro-active management strategy and (2) utilizes explicitly defined metrics of resistance and resilience to spruce beetle outbreaks.…”

Section: Discussionmentioning

confidence: 99%

“…However, by thinning from below, the structure shifted from a wide diameter distribution, containing small to large diameter trees in various gaps and densities, to more uniformly spaced large diameter spruce trees. Although, these large diameter spruces are attractive to the spruce beetle [18,40] they will produce large amounts of seeds and potentially supplement planted seedlings [28].…”

Section: Discussionmentioning

confidence: 99%

“…Engelmann spruce and subalpine fir have complementary life history strategies which allow for coexistence ( [12,33,[35][36][37][38][39][40], and references therein). Across the Rocky Mountains, the individual life histories of spruce and fir influence the structure.…”

Section: Study Speciesmentioning

confidence: 99%

“…The Schmid and Frye [25] spruce beetle risk rating uses four different metrics: physiographic location, QMD of spruce tree greater than 25.4 cm in dbh, stand basal area (m 2 ·ha −1 ), and proportion of the stand basal area (m 2 ·ha −1 ) that is spruce [40] ( Table 2). Values for each metric are rated as high (3), medium (2), or low (1) and the sum of the values is the stand risk rating.…”

Section: Resistancementioning

confidence: 99%

“…The proportion of stand that is spruce was calculated based on the proportion of live Engelmann spruce to total live basal area [40]. …”

Section: Spruce Beetle Risk Rating Systemmentioning

confidence: 99%

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If Long-Term Resistance to a Spruce Beetle Epidemic is Futile, Can Silvicultural Treatments Increase Resilience in Spruce-Fir Forests in the Central Rocky Mountains?

Windmuller-Campione

Long

2015

Forests

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Abstract:Within the Central Rocky Mountains, spruce beetle populations have the potential to rapidly transition from endemic to epidemic levels in the spruce-fir (Engelmann spruce and subalpine fir) forest type. Conventional management has focused on creating resistance to spruce beetle outbreaks by manipulating the overstory density and composition. Three silvicultural treatments, single tree selection, group selection, and shelterwood with reserves, were established in a spruce-fir forest in northern Utah with the goals of increasing both resistance and resilience to outbreaks. Resistance and resilience metrics were explicitly defined. Pre-harvest and two post-harvest measurements were used to assess how the different silvicultural treatments influenced the metrics. The shelterwood with reserves was the only treatment to meet both the resistance and resilience criteria. This treatment, while not traditionally used, created a stand structure and composition that will be most resilient to climate induced increases in spruce beetle caused tree mortality. However, there will be a trade-off in composition and structure, especially Engelmann spruce, after a spruce beetle epidemic because the created structure is more uniform with fewer groups and gaps than commonly observed in spruce-fir forests. With changing climatic conditions, proactive forest management, such as the shelterwood with reserves in the spruce-fir forest type, is the best method for increasing short-term resistance and long-term resilience to spruce beetle outbreaks. OPEN ACCESSForests 2015, 6 1158

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Study Speciesmentioning

confidence: 99%

Section: Resistancementioning

confidence: 99%

“…The proportion of stand that is spruce was calculated based on the proportion of live Engelmann spruce to total live basal area [40]. …”

Section: Spruce Beetle Risk Rating Systemmentioning

confidence: 99%

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If Long-Term Resistance to a Spruce Beetle Epidemic is Futile, Can Silvicultural Treatments Increase Resilience in Spruce-Fir Forests in the Central Rocky Mountains?

Windmuller-Campione

Long

2015

Forests

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Pre‐outbreak forest conditions mediate the effects of spruce beetle outbreaks on fuels in subalpine forests of Colorado

Mietkiewicz

Kulakowski

Veblen

2018

Ecological Applications

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Over the past 30 years, forest disturbances have increased in size, intensity, and frequency globally, and are predicted to continue increasing due to climate change, potentially relaxing the constraints of vegetation properties on disturbance regimes. However, the consequences of the potentially declining importance of vegetation in determining future disturbance regimes are not well understood. Historically, bark beetles preferentially attack older trees and stands in later stages of development. However, as climate warming intensifies outbreaks by promoting growth of beetle populations and compromising tree defenses, smaller diameter trees and stands in early stages of development now are being affected by outbreaks. To date, no study has considered how stand age and other pre-outbreak forest conditions mediate the effects of outbreaks on surface and aerial fuel arrangements. We collected fuels data across a chronosequence of post-outbreak sites affected by spruce beetle (SB) between the 1940s and the 2010s, stratified by young (<130 yr) and old (>130 yr) post-fire stands. Canopy and surface fuel loads were calculated for each tree and stand, and available crown fuel load, crown bulk density, and canopy bulk densities were estimated. Canopy bulk density and density of live canopy individuals were reduced in all stands affected by SB, though foliage loss was proportionally greater in old stands as compared to young stands. Fine surface fuel loads in young stands were three times greater shortly (<30 yr) following outbreak as compared to young stands not affected by outbreak, after which the abundance of fine surface fuels decreased to below endemic (i.e., non-outbreak) levels. In both young and old stands, the net effect of SB outbreaks during the 20th and 21st centuries reduced total canopy fuels and increased stand-scale spatial heterogeneity of canopy fuels following outbreak. Importantly, the decrease in canopy fuels following outbreaks was greater in young post-fire stands than in older stands, suggesting that SB outbreaks may more substantially reduce risk of active crown fire when they affect stands in earlier stages of development. The current study shows that the effects of SB outbreaks on forest structure and on fuel profiles are strongly contingent on pre-outbreak conditions as determined by pre-outbreak disturbance history.

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The relative importance of tree and stand properties in susceptibility to spruce beetle outbreak in the mid‐20th century

et al. 2016

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Citation: Bakaj, F., N. Mietkiewicz, T. T. Veblen, and D. Kulakowski. 2016. The relative importance of tree and stand properties in susceptibility to spruce beetle outbreak in the mid-20th century. Ecosphere 7(10):e01485. 10.1002/ecs2.1485Abstract. Tree susceptibility to potentially lethal agents is determined not only by attributes of individual trees, but also by neighborhood effects at a range of scales. For example, effects of disturbances on individual trees are often contingent on the size, configuration, and other properties of neighboring trees. Wildfires can modify postfire properties of individual trees as well as of entire forest stands, both of which can affect subsequent ecological processes, including subsequent disturbances. In recent years, much has been learned about how disturbances interact, but numerous questions concerning underlying mechanisms remain unresolved. For example, the relative importance of forest properties at different spatial scales in determining how fires affect forest susceptibility to subsequent disturbances is not well understood. This study explicitly compares the relative importance of tree vs. fine-scale neighborhood effects (e.g., stand properties at <7 m radii), on susceptibility to a 1940s' spruce beetle outbreak. Attributes of individual trees and of stand structure were spatially reconstructed at five 250-m 2 sites that were partly burned in the late 19th century and then affected by spruce beetle outbreak in the 1940s. Random Forest models and classification trees were used to compare the relative importance of variables for susceptibility to spruce beetle attack. Individual tree properties (diameter at breast height and age) were the most important predictors of susceptibility to the outbreak across all sites combined and at each of the sites individually. In contrast, neighborhood effects were poor predictors of susceptibility. This study suggests wildfires reduce susceptibility to outbreaks primarily by reducing the size of postfire live trees and only secondarily by modifying stand structure. One implication of this is that management strategies that aim to modify stand structure over large areas in order to reduce susceptibility to spruce beetle outbreaks may be unnecessarily intensive.

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Do tree and stand-level attributes determine susceptibility of spruce-fir forests to spruce beetle outbreaks in the early 21st century?

Cited by 43 publications

References 32 publications

If Long-Term Resistance to a Spruce Beetle Epidemic is Futile, Can Silvicultural Treatments Increase Resilience in Spruce-Fir Forests in the Central Rocky Mountains?

If Long-Term Resistance to a Spruce Beetle Epidemic is Futile, Can Silvicultural Treatments Increase Resilience in Spruce-Fir Forests in the Central Rocky Mountains?

Pre‐outbreak forest conditions mediate the effects of spruce beetle outbreaks on fuels in subalpine forests of Colorado

The relative importance of tree and stand properties in susceptibility to spruce beetle outbreak in the mid‐20th century

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