Species, Climate and Landscape Physiography Drive Variable Growth Trends in Subalpine Forests

Kelsey, Katharine C.; Redmond, Miranda D.; Barger, Nichole N.; Neff, Jason C.

doi:10.1007/s10021-017-0139-7

Cited by 22 publications

(27 citation statements)

References 70 publications

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“…After accounting for the percent of basal area lost, juveniles were growing faster in topographically wetter sites and sites at lower slope positions where temperatures are presumably warmer. However, faster growth rates of juvenile fir than spruce may be short‐lived if the effects of warming on adult fir growth are more deleterious than the effects on spruce growth (Kelsey et al ).…”

Section: Discussionmentioning

confidence: 99%

“…The subalpine zone of southern Colorado is characterized by a cool and moist climate (Romme et al ). Average annual temperatures range from 1.3° (northern plots) to 2.2°C (southern plots; 1970–2017, PRISM Climate Group ) and temperatures have increased by about 1°C over the past three decades (1975–2012; Kelsey et al ). Total mean annual precipitation ranges spatially from 510–1,300 mm with about 65% of precipitation falling as snow from October–April.…”

Section: Methodsmentioning

confidence: 99%

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Forest recovery following synchronous outbreaks of spruce and western balsam bark beetle is slowed by ungulate browsing

Andrus

Hart

Veblen

2020

Ecology

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Understanding how severe disturbances and their interactions affect forests is key to projecting ecological change under a warming climate. Substantial increases in some biotic disturbances, such as bark beetle outbreaks, in temperate forest ecosystemsmay compromise recovery to a forest vegetation type (i.e., physiognomic recovery or resilience), especially if subsequent biotic disturbances (e.g., herbivory) alter recovery mechanisms. From 2005 to 2017, severe outbreaks (>90% mortality) of spruce bark beetles (SB, Dendroctonus rufipennis) affected Engelmann spruce (Picea engelmannii) across 325,000 ha of spruce and subalpine fir (Abies lasiocarpa) forest in the southern Rocky Mountains, USA. Concurrently, an outbreak of western balsam bark beetle (WBBB, Dryocoetes confuses) infested subalpine fir across at least 47,000 of these hectares. We explored the capacity of 105 stands affected by one or two bark beetle outbreaks and browsing of juvenile trees by ungulates to return to a forest vegetation type in the context of pre-outbreak forest conditions and topography. Nine initial forest trajectories (i.e., at least several decades) were identified from four pre-outbreak forest types affected by three biotic disturbances that occurred at different spatial scales and severities. Most stands (86%) contained surviving nonhost adult trees in the main canopy (fir and aspen [Populus tremuloides]) and many surviving juveniles of all species, implying that they are currently on a trajectory for physiognomic recovery. Stands composed exclusively of large-diameter spruce were affected by a severe SB outbreak and were most vulnerable to a transition to a low-density forest, below regional stocking levels (<370 trees/ha). Greater pre-outbreak stand structural complexity and species diversity were key traits of stands with a higher potential for physiognomic recovery. However, all multispecies stands shifted in relative composition of the main canopy to nonhost species, suggesting low potential for compositional recovery over the next several decades. Most post-outbreak stands (86%) exceeded regional stocking levels with trees taller than the browse zone (<2 m). As such, ungulate browsing on over half of all juveniles will primarily affect the rate of infilling of the forest canopy and preferential browsing of more palatable species will influence the composition of the future forest canopy.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Forest recovery following synchronous outbreaks of spruce and western balsam bark beetle is slowed by ungulate browsing

Andrus

Hart

Veblen

2020

Ecology

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“…However, our results concur with the observed lack of a CO 2 -induced growth response in mature natural stands illustrated via manipulative experiment (Körner et al, 2005), inventories (Chen, Luo, Reich, Searle, & Biswas, 2016) and tree rings (Camarero et al, 2015;Gedalof & Berg, 2010;Groenendijk et al, 2015;Reed, Ballantyne, Cooper Leila, & Sala, 2018;van der Sleen et al, 2014). Other recent large-scale analyses reveal a high degree of heterogeneity in growth responses to elevated CO 2 (Charney, D., Babst, F., Poulter, B., Record, S., Trouet, V., M., Frank, D., Evans, M., E., Evans, M., E., Evans, M., E., Evans, M., & E. K., 2016; Girardin et al, 2016;Kelsey, Redmond, Barger, & Neff, 2018;Tei et al, 2017). This, as well as fundamental theory on the limits to tree growth, indicates that a CO 2 fertilization effect is unlikely to be ubiquitous and that making such an assumption might lead to inappropriate predictions.…”

Section: Discussionmentioning

confidence: 99%

Tree rings provide no evidence of a CO₂ fertilization effect in old‐growth subalpine forests of western Canada

Hararuk

Campbell

Antos³

et al. 2019

Global Change Biology

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Atmospheric CO2 concentrations are now 1.7 times higher than the preindustrial values. Although photosynthetic rates are hypothesized to increase in response to rising atmospheric CO2 concentrations, results from in situ experiments are inconsistent in supporting a CO2 fertilization effect of tree growth. Tree‐ring data provide a historical record of tree‐level productivity that can be used to evaluate long‐term responses of tree growth. We use tree‐ring data from old‐growth, subalpine forests of western Canada that have not had a stand‐replacing disturbance for hundreds of years to determine if growth has increased over 19th and 20th centuries. Our sample consisted of 5,858 trees belonging to five species distributed over two sites in the coastal zone and two in the continental climate of the interior. We calculated annual increments in tree basal area, adjusted these increments for tree size and age, and tested whether there was a detectable temporal trend in tree growth over the 19th and 20th centuries. We found a similar pattern in 20th century growth trends among all species at all sites. Growth during the 19th century was mostly stable or increasing, with the exception of one of the coastal sites, where tree growth was slightly decreasing; whereas growth during the 20th century consistently decreased. The unexpected decrease in growth during the 20th century indicates that there was no CO2 fertilization effect on photosynthesis. We compared the growth trends from our four sites to the trends simulated by seven Earth System Models, and saw that most of the models did not predict these growth declines. Overall, our results indicate that these old‐growth forests are unlikely to increase their carbon storage capacity in response to rising atmospheric CO2, and thus are unlikely to contribute substantially to offsetting future carbon emissions.

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“…The discovery of a potential growth divergence based on aspect led us to the research question addressed in this study: What is the potential for differential responses in radial growth and climate/growth relationships over time between groupings of alpine larch trees exposed to identical macroenvironmental conditions but different microenvironmental conditions related to aspect? The leading drivers of microenvironmental differences in relation to aspect are solar radiation and associated soil moisture fluctuations (Kelsey et al 2017). Southern aspects in the northern hemisphere and northern aspects in the southern hemisphere generally experience drier conditions because of longer and more intense exposure to incoming solar radiation.…”

Section: Introductionmentioning

confidence: 99%

“…Southern aspects in the northern hemisphere and northern aspects in the southern hemisphere generally experience drier conditions because of longer and more intense exposure to incoming solar radiation. In the southwestern Colorado Rocky Mountains, Kelsey et al (2017) identified negative trends in radial growth for subalpine fir (Abies lasiocarpa [Hook.] Nutt.)…”

Section: Introductionmentioning

confidence: 99%

Divergent growth rates of alpine larch trees (Larix lyallii Parl.) in response to microenvironmental variability

Montpellier

Soulé

Knapp

et al. 2018

Arctic, Antarctic, and Alpine Research

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In this study we explore radial growth rates and climatic responses of alpine larch trees (Larix lyallii Parl.) growing in high elevations of the northern Rocky Mountains of Montana, USA. We examine responses between two stands of alpine larch that are separated by less than one kilometer and are growing at similar elevations, but with different aspects. Radial growth rates from trees sampled on the southern aspect of Trapper Peak (TPS) were largely controlled by January snow-water equivalent, while summer maximum temperature was the principal radial-growth driver for trees sampled on the northern aspect of Trapper Peak (TPN). Following the coldest summer (1993) in the century-long instrumental climate record, the radial growth at TPN became greater than at TPS and was the reverse of what occurred pre-1993. We posit that an upward trend in maximum summer temperature is preferentially benefitting the trees growing on the north-facing TPN site by extending the growing season and causing earlier snowmelt, and this has caused the growth rate divergence during the past two decades. As such, our study illustrates that the growth-divergence phenomenon noted in other high-elevation species, whereby macroenvironmental changes are eliciting responses at the microenvironmental level, occurs within stands of alpine larch growing in western Montana.

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Species, Climate and Landscape Physiography Drive Variable Growth Trends in Subalpine Forests

Cited by 22 publications

References 70 publications

Forest recovery following synchronous outbreaks of spruce and western balsam bark beetle is slowed by ungulate browsing

Forest recovery following synchronous outbreaks of spruce and western balsam bark beetle is slowed by ungulate browsing

Tree rings provide no evidence of a CO₂ fertilization effect in old‐growth subalpine forests of western Canada

Divergent growth rates of alpine larch trees (Larix lyallii Parl.) in response to microenvironmental variability

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Species, Climate and Landscape Physiography Drive Variable Growth Trends in Subalpine Forests

Cited by 22 publications

References 70 publications

Forest recovery following synchronous outbreaks of spruce and western balsam bark beetle is slowed by ungulate browsing

Forest recovery following synchronous outbreaks of spruce and western balsam bark beetle is slowed by ungulate browsing

Tree rings provide no evidence of a CO2 fertilization effect in old‐growth subalpine forests of western Canada

Divergent growth rates of alpine larch trees (Larix lyallii Parl.) in response to microenvironmental variability

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Tree rings provide no evidence of a CO₂ fertilization effect in old‐growth subalpine forests of western Canada