Impacts of Douglas-fir bark beetle (Dendroctonus pseudotsugae) sanitation harvesting within Old Growth Management Areas (OGMAs) of the Central Cariboo and 100 Mile House forest districts were measured in the field at 22 sites harvested in the winter of 2005/06. These impacts were then analyzed and compared against predicted impacts of alternative treatment scenarios developed for sites based on infestation size. Impact predictions were based on a number of assumptions. Two key assumptions were: 1) trap trees would be felled at a ratio of one trap tree to every four current attack trees identified through ground probing; and 2) trap trees would be placed 200 m from the far reaches of an infestation site. Impacts of the actual harvest treatment were shown to be considerably higher than predicted impacts of alternative treatments. Analysis of a trap tree treatment on all sites, regardless of infestation size and using no minimum number of trap trees, showed an 82% reduction in the mean number of trees cut. The analysis also showed that the mean length of skid trails was reduced, primarily as a result of locating trap trees outside of OGMAs or reducing the length of new skid trails developed. On average, fewer trees were predicted to be cut under trap tree treatment compared to the harvesting treatment. Alternative treatment scenarios were developed to predict a range of possible impact reductions based on infestation size. Recommendations are provided for improving the monitorability of sanitation harvesting.
Nowotny Applied Biological Services. 2006. Douglas-fir bark beetle sanitation harvest assessments in the Central Cariboo and 100 Mile House Forest Districts. Ministry of Environment