Droughty times in mesic places: factors associated with forest mortality vary by scale in a temperate subalpine region

Understanding how drivers of ecological disturbance operate across scales is important in an era of increasing disturbance activity. Severe and extensive Dendroctonus bark beetle outbreaks across western North America have left in their wake dominance by shade‐tolerant and commonly late‐seral trees...

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Bibliographic Details
Published in:Ecosphere (Washington, D.C) D.C), 2021-01, Vol.12 (1), p.n/a
Main Authors: Harvey, Brian J., Andrus, Robert A., Battaglia, Mike A., Negrón, José F., Orrego, Alexandra, Veblen, Thomas T.
Format: Article
Language:English
Subjects:
Abies lasiocarpa
Bark
conifer forest
Disturbance
disturbance ecology
Drought
Dryocoetes confusus
Epidemics
Forests
Mortality
Pathogens
rocky mountains
subalpine fir decline
Topography
tree mortality
Trees
Variables
western balsam bark beetle
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Summary:Understanding how drivers of ecological disturbance operate across scales is important in an era of increasing disturbance activity. Severe and extensive Dendroctonus bark beetle outbreaks across western North America have left in their wake dominance by shade‐tolerant and commonly late‐seral trees such as subalpine fir (Abies lasiocarpa), which can foster resilience of forest cover. However, subalpine fir decline (SFD) is a poorly understood phenomenon that has killed trees across millions of hectares in western North America with unknown consequences for future forest resilience. How different factors (e.g., climate, topography, host‐tree characteristics, and abundance) govern SFD presence and severity across spatial scales from individual trees to a subcontinental scale has not been explored in a single framework. Here, we combine broad‐scale geospatial data on SFD occurrence, stand‐scale field data on SFD severity, and fine‐scale individual tree data on mortality to test the relative importance of factors related to SFD across spatial scales spanning >10 orders of magnitude (10 M hectares). At the broadest scale (subcontinental, ~25 M ha), annual areal extent of SFD over time increased sharply with antecedent drought. At regional‐ (~6 M ha) and stand‐ (0.1–0.25 ha) scales, the occurrence and severity of SFD were spatially associated with more mesic topographic positions and greater host‐tree abundance. Finally, at the individual tree‐ and tree‐neighborhood‐ (
ISSN:2150-8925
2150-8925
DOI:10.1002/ecs2.3318