Canadian Forest Service Publications
Mountain Pine Beetle Dispersal through Managed and Unmanaged Landscapes. 2009. Reid, M. Natural Resources Canada, Canadian Forest Service, Pacific Forestry Centre, Victoria, BC. Mountain Pine Beetle Working Paper 2008-17. 17 p.
Issued by: Pacific Forestry Centre
Catalog ID: 29221
Dispersal of mountain pine beetles, Dendroctonus ponderosae, is expected to be influenced by the energetic costs of dispersal that in turn may be influenced by the species composition and tree density of forest stands. In Banff and Kootenay National Parks, three times as many mountain pine beetles were captured in pheromone-baited traps within lodgepole pine stands than within white spruce stands, with more beetles captured in Kootenay than in Banff National Parks. Clearcuts and thinned stands showed little reduction in mountain pine beetles 90 m from the edge, except in a clearcut at the sapling stage. Two other bark beetles, Ips pini and Pityogenes knechteli, showed significant reductions in clearcuts relative to adjacent intact stands, but not in thinned stands. These species tended to have highest abundances at the edge of intact stands, while this pattern was not clearly seen for mountain pine beetles. Overall, while bark beetles tend to occur in lower numbers in non-host stands, they are still commonly found in such stands.
The effects of dispersal costs may explain discrepancies in metrics used to evaluate the success of a management zone in Banff National Park, but these may be more related to reductions in population size than to stand characteristics. In the management zone east of Banff, where all detected green-attacked trees were removed since 2002, the area affected by mountain pine beetles (measured as area of red attack) changed little compared to the monitoring zones, but the number of 25 ha cells with some red attack was greatly reduced. Trap catches in the two zones revealed that there were fewer beetles captured and they were in poorer body condition in the management zone than in the monitoring zone. This could not be attributed to poorer production in the management zone, and instead is consistent with the idea that reduced population size limited the long-distance dispersal success of mountain pine beetles resulting in beetles in poorer condition. Thus, while the costs of dispersal may influence the spread of mountain pine beetles, these costs appear to depend more on population size than on stand attributes.