Cross-scale Drivers of Natural Disturbances Prone to Anthropogenic Amplification: The Dynamics of Bark Beetle Eruptions

Raffa, Kenneth F.; Aukema, Brian H.; Bentz, Barbara; Carroll, Allan L.; Hicke, Jeffrey A.; Turner, Monica G.; Romme, William H.

doi:10.1641/b580607

Cited by 1,489 publications

(1,512 citation statements)

References 68 publications

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“…In the Rocky Mountains of North America, bark beetles have become a major agent of change [Raffa et al, 2008]. Although mountain pine beetle (Dendroctonus ponderosae) often grabs headlines due to 12,700,000 ha of forest affected in Canada plus another 3,300,000 ha in the western United States [Natural Resources Canada, 2010;USDA Forest Service, 2012], spruce beetle (Dendroctonus rufipennis) is the major insect disturbance in the subalpine spruce-fir forests of North America.…”

Section: Introductionmentioning

confidence: 99%

Ecosystem CO₂/H₂O fluxes are explained by hydraulically limited gas exchange during tree mortality from spruce bark beetles

et al. 2014

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Disturbances are increasing globally due to anthropogenic changes in land use and climate. This study determines whether a disturbance that affects the physiology of individual trees can be used to predict the response of the ecosystem by weighing two competing hypothesis at annual time scales: (a) changes in ecosystem fluxes are proportional to observable patterns of mortality or (b) to explain ecosystem fluxes the physiology of dying trees must also be incorporated. We evaluate these hypotheses by analyzing 6 years of eddy covariance flux data collected throughout the progression of a spruce beetle (Dendroctonus rufipennis) epidemic in a Wyoming Engelmann spruce (Picea engelmannii)-subalpine fir (Abies lasiocarpa) forest and testing for changes in canopy conductance (g c ), evapotranspiration (ET), and net ecosystem exchange (NEE) of CO 2 . We predict from these hypotheses that (a) g c , ET, and NEE all diminish (decrease in absolute magnitude) as trees die or (b) that (1) g c and ET decline as trees are attacked (hydraulic failure from beetle-associated blue-stain fungi) and (2) NEE diminishes both as trees are attacked (restricted gas exchange) and when they die. Ecosystem fluxes declined as the outbreak progressed and the epidemic was best described as two phases: (I) hydraulic failure caused restricted g c , ET (28 ± 4% decline, Bayesian posterior mean ± standard deviation), and gas exchange (NEE diminished 13 ± 6%) and (II) trees died (NEE diminished 51 ± 3% with minimal further change in ET to 36 ± 4%). These results support hypothesis b and suggest that model predictions of ecosystem fluxes following massive disturbances must be modified to account for changes in tree physiological controls and not simply observed mortality.

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Section: Introductionmentioning

confidence: 99%

Ecosystem CO₂/H₂O fluxes are explained by hydraulically limited gas exchange during tree mortality from spruce bark beetles

et al. 2014

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“…In such places, gradual changes in climate may cross thresholds that cause rapid changes in tree growth, as well as increased susceptibility to attack from insects and pathogens (Raffa et al 2008;Bentz et al 2010;Yan and Niu 2008;Ayres and Lombardero 2000;Sturrock et al 2011).…”

Section: Introductionmentioning

confidence: 99%

Recent reduction in the frequency of frost accounts for most of the increased growth of a high elevation spruce forest in northwestern China

Waring

Gao

2016

Trees

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Key message Using process-based models in combination with dendrochronological measurements provides a way to explain recent increased tree growth in northwestern China. Abstract Dendrochronological studies of tree rings in a 250-year-old Qinghai spruce (Picea crassifolia) forest in the Qilian Mountains of northwestern China indicate a 60 % sustained increase in tree-ring growth between 1980 and 2009 compared with any time since 1785. Over the same period, the maximum, minimum, and average temperatures all increased by nearly 2°C during the growing season (May through September), the frequency of frost decreased 18 days, precipitation remained unchanged, while atmospheric concentrations of CO 2 increased by 48 ppm. To explain how the changes in climatic variables might cause the increase in tree growth, we parameterized a process-based growth model (3-PG, physiological processes predicting growth) with values from the literature and performed a series of sensitivity tests. The results of our analysis indicated that a reduction in frost frequency during the growing season, which allows stomata to remain open, enhanced gross photosynthesis by 42 %. Up to a 20 % increase in P G could be attributed to rising atmospheric CO 2 between 1980 and 2009, with half of this attributed to increased light interception from a simulated 0.4 increase in canopy leaf area index. The increase in average and maximum temperatures had little direct effect on gross photosynthesis with the optimum temperature set between 9 and 10°C. Indirectly, the increase in monthly average minimum temperature during the growing season, although small, crossed a threshold that reduced the impact of frost. Our analyses show the value of combining dendrochronological measurements with a process-based model to gain a more holistic understanding of how environmental factors interact to affect tree growth.

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“…Typically, small populations generate a scattered pattern because the beetles search for suitable hosts, while beetles in large populations tend to infest the trees in a closer vicinity (Kausrud et al 2011;Hlásny & Turčáni 2013). Large populations might tend to collapse after a several-year period of the outbreak culmination because of the effect of diverse density dependent regulation mechanisms (Raffa et al 2008). Therefore, the coefficient of affinity we used in the current study should change in time depending on a number of factors (e.g.…”

Section: Discussionmentioning

confidence: 99%

Effect of different tree mortality patterns on stand development in the forest model SIBYLA

Trombik¹,

Barka²,

Hlásny³

2016

Forestry Journal

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Forest mortality critically affects stand structure and the quality of ecosystem services provided by forests. Spruce bark beetle (Ips typographus) generates rather complex infestation and mortality patterns, and implementation of such patterns in forest models is challenging. We present here the procedure, which allows to simulate the bark beetle-related tree mortality in the forest dynamics model Sibyla. We explored how sensitive various production and stand structure indicators are to tree mortality patterns, which can be generated by bark beetles. We compared the simulation outputs for three unmanaged forest stands with 40, 70 and 100% proportion of spruce as affected by the disturbance-related mortality that occurred in a random pattern and in a patchy pattern. The used tree species and age class-specific mortality rates were derived from the disturbance-related mortality records from Slovakia. The proposed algorithm was developed in the SQLite using the Python language, and the algorithm allowed us to define the degree of spatial clustering of dead trees ranging from a random distribution to a completely clustered distribution; a number of trees that died in either mode is set to remain equal. We found significant differences between the long-term developments of the three investigated forest stands, but we found very little effect of the tested mortality modes on stand increment, tree species composition and diversity, and tree size diversity. Hence, our hypothesis that the different pattern of dead trees emergence should affect the competitive interactions between trees and regeneration, and thus affect selected productivity and stand structure indicators was not confirmed.

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Cross-scale Drivers of Natural Disturbances Prone to Anthropogenic Amplification: The Dynamics of Bark Beetle Eruptions

Cited by 1,489 publications

References 68 publications

Ecosystem CO₂/H₂O fluxes are explained by hydraulically limited gas exchange during tree mortality from spruce bark beetles

Ecosystem CO₂/H₂O fluxes are explained by hydraulically limited gas exchange during tree mortality from spruce bark beetles

Recent reduction in the frequency of frost accounts for most of the increased growth of a high elevation spruce forest in northwestern China

Effect of different tree mortality patterns on stand development in the forest model SIBYLA

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Cross-scale Drivers of Natural Disturbances Prone to Anthropogenic Amplification: The Dynamics of Bark Beetle Eruptions

Cited by 1,489 publications

References 68 publications

Ecosystem CO2/H2O fluxes are explained by hydraulically limited gas exchange during tree mortality from spruce bark beetles

Ecosystem CO2/H2O fluxes are explained by hydraulically limited gas exchange during tree mortality from spruce bark beetles

Recent reduction in the frequency of frost accounts for most of the increased growth of a high elevation spruce forest in northwestern China

Effect of different tree mortality patterns on stand development in the forest model SIBYLA

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Ecosystem CO₂/H₂O fluxes are explained by hydraulically limited gas exchange during tree mortality from spruce bark beetles

Ecosystem CO₂/H₂O fluxes are explained by hydraulically limited gas exchange during tree mortality from spruce bark beetles