PARENT SESSION
Poster Session #55: Plant-Animal Interactions II.
Thursday, August 8. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC
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Patterns of spruce bark beetle (Dendroctonus rufipennis) spread within white spruce (Picea glauca) stands.
Doak, Pat*,1, 1 Institute of Arctic Biology, Fairbanks, AK
ABSTRACT- Patterns of bark beetle attack and spread will be mediated by beetle response to characteristics of host individuals, the location of these hosts in relation to conspecifics, and the spatial arrangement of host populations. The goal of the current research is to further our understanding of Dendroctonus rufipennis outbreak patterns in Alaskan boreal forests. The research combines studies of individual host traits with detailed information on the location, characteristics, and condition of conspecific neighbors, to better understand the factors contributing to risk of bark beetle attack and spread of epidemics. The study was conducted in the Kennicott Valley, Wrangell-St. Elias National Park and Preserve, Alaska. In this region Dendroctonus rufipennis epidemics leading to tree mortality first appeared in 1989. Five sites were arrayed along the north-south axis of the valley and two 30 m radius study plots were haphazardly located at each site. I mapped the locations of each white spruce in the plot, evaluated condition especially as related to bark beetle attack, measured dbh, and took one or more increment core samples. I was then able to calculate growth rates, tree ages, and, by crossdating trees, the year of death for those trees killed by bark beetles. Bark beetle induced mortality varied between 15 and 80 % in the sampled stands although stands have similar size and age distributions. While killed trees are often larger and older than surviving trees, slow radial growth was the best predictor of beetle induced mortality. In addition to the influence that individual characteristics have on susceptibility to beetle attack, I found that both the presence of neighbors attacked during the same season and the presence of neighbors attacked one to two years previously influence a trees survival probability.
KEY WORDS: bark beetle, boreal forest, Dendroctonus rufipennis