PARENT SESSION
Oral Session #78: Insect Population and Community Ecology. Presiding: R. Denno.
Friday, August 10, 2001. 8:00 AM to 11:45 AM. Hall of Ideas I.
The effect of landscape heterogeneity due to forestry on the settlement patterns of a bark beetle .
Park, Jane1, Reid, Mary1, 1
ABSTRACT- Logging may influence habitat of saproxylic insects such as Polyraphus rufipennis, a bark beetle that inhabits freshly dead spruce. Following harvest, substantial amounts of freshly dead woody debris remain on site, that may be unevenly distributed on the landscape. However, it is uncertain what effect these landscape changes will have on bark beetles. Our study examined the effects of different harvesting regimes on the settlement of the four-eyed spruce beetle P. rufipennis. The project design consisted of three replicates of four stand types (aspen dominated, aspen dominated with conifer understorey, mixed, and conifer dominated). Within each stand type, four harvest levels were examined: 10% retention, 20%, 50%, and uncut control. Subsamples of all available habitat (spruce logs > 10 cm diameter) in each compartment were measured and examined for the presence or absence of beetles. If beetles were present, density within an 800cm2 area was recorded. We found that settlement density depended on habitat quality (as measured by diameter of logs) and the surrounding stand type (ANOVA, R2=0.10, p=0.0002). Settlement densities tended to be lowest in conifer dominated stands where diameter was the largest. These data indicate the heterogeneity of the landscape may influence the settlement patterns of P. rufipennis. Furthermore, P. rufipennis may be settling according to recent source-sink models of habitat selection, where individuals choose habitat according to habitat quality and availability to minimize search costs.
KEY WORDS: Polygraphus rufipennis, logging, settlement, landscape