Canadian Forest Service Publications
Change in wood quality and fall rate of trees up to ten years after death from mountain pine beetle. 2009. Lewis, K.J.; Thompson, D. Natural Resources Canada, Canadian Forest Service, Pacific Forestry Centre, Victoria, BC. Mountain Pine Beetle Working Paper 2008-30. 30 p.
Available from: Pacific Forestry Centre
Catalog ID: 29365
Despite the history of mountain pine beetle outbreaks in British Columbia, including the outbreak in the mid 1980s that affected timber supply in the Quesnel Timber Supply Area, little was known about the post-mortality rate of deterioration of wood quality and quantity, and the rate of change in stand structure due to fall of dead trees. In this stuidy, we used dendrochronology to crossdate pine killed by mountain pine beetle. We determined the exact year of mortality and characterized decay and degradation in factors of wood quality and quantity over time. Over 550 trees were sampled and successfully cross-dated, 126 of these had been dead for more than 6 years. At the stand level, 0.25% of the pine that had been dead for 5 years or less had fallen. In stands where trees were killed between 6 and 10 years ago, the average fall rate was 28%, ranging from 0 to 60% per plot. Most trees did not start to fall until 8 years post-mortality. No relationship was found between rate of fall and tree size, although dry sites had a higher rate of tree fall than wet sites. We found that change in moisture content of the wood was the main driver behind the changes in wood properties. Dependent variables included checking (number and depth), bluestain depth, saprot, and damage caused by wood borers. A small collection of biophysical variables (time-since-death, tree size (DBH), height of sample, and growth rate) explained the variation in dependent variables, and a number of regression models were built to predict the dependent variables. Biogeoclimatic unit and soil moisture regime were not important predictors of decay and degrade in this study, except for development of saprot at the base of the trees. Significant change in the above factors occurred within the first 1-2 post-mortality years and varied with position along the stem and with the size of the tree, followed by a period of relative stability in wood properties until 8 or more years post-mortality, when dead trees start to fall.