Spruce beetle outbreaks and traumatic resin ducts

Authors: Matthew Bekker*, Brigham Young University, R Justin DeRose, US Forest Service
Topics: Physical Geography, Biogeography, Paleoenvironmental Change
Keywords: dendrochronology, tree rings, biogeography, insects
Session Type: Poster
Day: 4/11/2018
Start / End Time: 8:00 AM / 9:40 AM
Room: Napoleon Foyer/Common St. Corridor, Sheraton, 3rd Floor
Presentation File: No File Uploaded

The formation of traumatic resin ducts (TRDs) represents an important induced defense in woody plants that enhances
oleoresin production and flow in response to environmental perturbations. Resin ducts are relatively rare in Picea spp., so the occurrence and strength of resin ducts, in particular TRDs, in annually resolved rings can be used to reconstruct mechanical damage associated with natural disturbances. We documented the consistency and strength of resin ducts in paired Engelmann spruce (Picea Engelmannii Parry ex Engelm.) trees with and without clear evidence of attack (e.g. pitch tubes) from a recent spruce beetle outbreak at the TW Daniels Experimental Forest in northern Utah. The presence of TRDs, defined as resin ducts aligned tangentially and arranged compactly, indicated mechanical damage associated with epidemic spruce beetle (Dendroctonus rufipennis (Kirby)) populations. TRD prevalence during the outbreak was significantly higher than over tree lifespans. All other metrics characterizing tree vigor (diameter, age, ring width, and basal area increment) were not significantly different between attacked and non-attacked trees. Because TRD production in our Engelmann spruce was exceedingly rare, this discovery represents a new line of tree-ring-based evidence that can be used to reconstruct past spruce beetle outbreaks.

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