Alpine treeline ecotones are potential refugia for a montane pine species threatened by bark beetle outbreaks

Maher, Colin; Millar, Constance I.; Affleck, David L. R.; Keane, Robert E.; Sala, Anna; Tobalske, Claudine; Larson, Andrew J.; Nelson, Cara R.

doi:10.1002/eap.2274

Cited by 6 publications

(4 citation statements)

References 77 publications

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“…Higher temperatures are known to favor mountain pine beetle activity at its northernmost latitudes and at the highest elevations in southerly latitudes, including much of California (Amman et al, 1977). Population models suggest beetle outbreaks may become increasingly frequent at higher elevations and latitudes as the climate continues to warm (Bentz et al, 2010), though the shrub‐like mats that WBP tends to form on high‐elevation exposed ridgetops (the “krummholz” growth form) lack the large boles that mountain pine beetles preferentially attack (Perkins & Roberts, 2003; Shanahan et al, 2016) and may serve as refugia from beetles (Maher et al, 2021). Extreme cold snaps and lack of host trees are identified as primary factors in stopping mountain pine beetle outbreaks in the US northern Rocky Mountains (Keane et al, 2012), where warmer winters, in particular, have been suggested to promote mountain pine beetle persistence (Logan & Powell, 2001).…”

Section: Introductionmentioning

confidence: 99%

Temperature is positively associated with tree mortality in California subalpine forests containing whitebark pine

2023

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Whitebark pine (Pinus albicaulis Engelm.) is a keystone high-elevation tree species occurring across much of western North America, yet it has been listed as threatened under the US Endangered Species Act due to rapid population declines and extensive ongoing pressures from white pine blister rust (Cronartium ribicola), mountain pine beetle (Dendroctonus ponderosae), and increasing temperature and aridity associated with climate change.Past research has shown that whitebark pine mortality is more likely in hotter and drier sites, but no broad-extent analyses spanning multiple ecoregions have directly quantified the relationship between mortality probability and its environmental drivers at a fine spatial scale. To address this gap, we used spatially continuous high-resolution (30 m) maps of mortality in California produced by a remote sensing-based change detection algorithm, and we developed generalized additive models to explain this mortality variability using relevant biophysical variables. We found that maximum daily temperature was strongly positively associated with mortality intensity and that mortality was also generally more intense in sites with greater solar exposure (e.g., south-facing slopes). Our results support the interpretation that as climate warms and aridity increases, populations in "trailing edge" (i.e., hot, dry) sites are most vulnerable. The environmental relationships we quantify will aid in identifying the locations and environments with the greatest risk of future mortality as well as those likely to serve as refugia.

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Section: Introductionmentioning

confidence: 99%

Temperature is positively associated with tree mortality in California subalpine forests containing whitebark pine

2023

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“…Recent studies also found that the alpine treeline ecotone can provide potential refugia for some threatened plant species [77]. Tree encroachment within the treeline ecotone may lead to a shift in species' relative abundances and functional diversity, possibly affecting alpine community assembly patterns [78]. Therefore, the possible implications of alpine treeline changes for the Tibetan Plateau ecosystems are worth special attention.…”

Section: Discussionmentioning

confidence: 99%

Heterogeneous Responses of Alpine Treelines to Climate Warming across the Tibetan Plateau

Wang

Ren

et al. 2022

Forests

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The Tibetan Plateau hosts a continuous distribution of alpine treelines from the Qilian Mountains to the Hengduan Mountains and the Himalaya Mountains. However, not much is known about the broadscale alpine treeline dynamics and their responses to climate warming across the Tibetan Plateau. Herein, we collected a total of 59 treeline sites across different forest regions of the Tibetan Plateau and the related field data (i.e., upward advance magnitude, tree recruitment and height growth), expansion potential (i.e., elevational difference between the current treeline and the tree species line (EP)) and vegetation TI (an index of species interactions) from the published references. Site characteristics (e.g., elevation, slope and aspect) and the related environmental factors were used to analyze the relationships between treeline shifts and environmental variables. Despite increases in the recruitment and growth of trees at most treeline sites, alpine treeline positions showed heterogeneous responses to climate warming. Most treelines advanced over the last century, while some treelines showed long-term stability. EP was significantly and positively linked to the summer warming rate and treeline shifts, suggesting that the position of current tree species line is of crucial importance in evaluating treeline dynamics under climate change. In addition, warming-induced treeline advances were modulated by plant–plant interactions. Overall, this study highlighted the heterogeneous responses of regional-scale alpine treelines to climate warming on the Tibetan Plateau.

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“…For instance, Redmond et al (2019) found that resin duct area decreased during years of increased cone production in piñon pine (Pinus edulis), while no discernable tradeoffs with growth were detected. Growth form could also be an important factor for long-term whitebark pine persistence as research has demonstrated lower mortality rates (Maher et al, 2020) and differing growth responses to climate (Millar et al, 2020) in krummholz whitebark pine trees relative to full-stem trees growing at treeline. While our study was not explicitly designed to test for such interactions, future studies could investigate relationships between exposure to white pine blister rust and insect-pathogen complexes on resin duct development and within-tree resource allocation patterns, and to quantify resin duct characteristics of krummholz vs. full-stem whitebark pine trees.…”

Section: Whitebark Pine Growth and Resin Duct Morphology Have Unique ...mentioning

confidence: 99%

Increased whitebark pine (Pinus albicaulis) growth and defense under a warmer and regionally drier climate

Kichas

Pederson²,

Hood³

et al. 2023

Front. For. Glob. Change

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IntroductionTree defense characteristics play a crucial role in modulating conifer bark beetle interactions, and there is a growing body of literature investigating factors mediating tree growth and resin-based defenses in conifers. A subset of studies have looked at relationships between tree growth, resin duct morphology and climate; however, these studies are almost exclusively from lower-elevation, moisture-limited systems. The relationship between resin ducts and climate in higher-elevation, energy-limited ecosystems is currently poorly understood.MethodsIn this study, we: (1) evaluated the relationship between biological trends in tree growth, resin duct anatomy, and climatic variability and (2) determined if tree growth and resin duct morphology of whitebark pine, a high-elevation conifer of management concern, is constrained by climate and/or regional drought conditions.ResultsWe found that high-elevation whitebark pine trees growing in an energy-limited system experienced increased growth and defense under warmer and regionally drier conditions, with climate variables explaining a substantive proportion of variation (∼20–31%) in tree diameter growth and resin duct anatomy.DiscussionOur results suggest that whitebark pine growth and defense was historically limited by short growing seasons in high-elevation environments; however, this relationship may change in the future with prolonged warming conditions.

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Alpine treeline ecotones are potential refugia for a montane pine species threatened by bark beetle outbreaks

Abstract: 2021. Alpine treeline ecotones are potential refugia for a montane pine species threatened by bark beetle outbreaks. Ecological Applications 31(3):e02274.

Cited by 6 publications

References 77 publications

Temperature is positively associated with tree mortality in California subalpine forests containing whitebark pine

Temperature is positively associated with tree mortality in California subalpine forests containing whitebark pine

Heterogeneous Responses of Alpine Treelines to Climate Warming across the Tibetan Plateau

Increased whitebark pine (Pinus albicaulis) growth and defense under a warmer and regionally drier climate

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