Abstract
The recent outbreak of native bark beetles in western North America is unprecedented in severity and scale, at least during the historical period. The aim of this work is to develop a proxy-based methodology to understand how bark beetle disturbances are recorded in lake sediments. Three hypotheses are tested to determine how the ecological impacts of severe spruce beetle (Dendroctonus rufipennis) disturbances are recorded following mortality of Engelmann spruce (Picea engelmannii). Outbreaks are hypothesized to: (1) decrease the ratio of spruce to fir pollen; (2) increase soil erosion and mobilize terrestrial C; and (3) leach foliar N, enhancing algal productivity. To test these hypotheses, sediment cores from spruce beetle-affected basins were analyzed for pollen, insect remains, organic and minerogenic content, and isotopic and elemental concentrations. The dataset was tested statistically using generalized linear mixed models (GLMMs) to determine if the response variables differed significantly between outbreak and non-outbreak periods.
Highlights
The ongoing native bark beetle outbreak in west‐ ern North America has affected over 47,000,000 ha of coniferous forest (Raffa et al 2008)
The geochemical and elemental analyses. Despite their obvious ecological and economic significance, surprisingly little is known about the recurrence and ecological role of native bark bee‐ tles prior to recent centuries
In the thirty sediment cores that were screened for bark beetle remains, no elytra or head capsules were recovered in correspon‐ dence with documented outbreaks
Summary
The ongoing native bark beetle outbreak in west‐ ern North America has affected over 47,000,000 ha of coniferous forest (Raffa et al 2008). The so‐ cial, aesthetic, and economic losses combined ex‐ ceed those of wildfire and other forest distur‐ bances (Logan et al 2003). In addition to climate warming, landscape and land use history are important in explaining the intensity of the recent outbreaks Model fore‐ casts indicate that prolonged warming during the 21st century will enable irruptive beetle popula‐ tions in ecosystems where they previously were limited by climate (Bentz et al 2010)
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