In 2005, 208 polygons (stands) and 1051 TSP were sampled in age class 1 to 8 in the SBSdk, SBSdw2, SBSdw3, and SBSmc in the central BC interior. These sub-zones account for 35 percent of Prince George TSA timber harvesting land base. The objectives were to i) quantify mountain pine beetle (MPB) attack, ii) document changes in stand attributes of pine dominated stands following MPB attack and iii) assess the potential of stand development after MPB attack without management intervention. About 4.5 percent of the trees < 10.0 cm at dbh were attacked and attack rates > 75 percent were observed for trees with dbh = 20 cm. There was a weak but significant relationship when stand densities increased, MPB attack rates decreased. Vigorous, widely spaced, young stands may be at a greater risk to MPB attack than was previously believed. MPB attack increased with age class. It reached maximum levels of 80 percent in age class 6 to 8. Attack rates were less than 10 percent in age class 1 but almost 30 percent in age class 2. The attack rates in age class 1 to 3 far exceed the rates used in current timber supply calculations. Green attack was dominant in age class 1 and 2 but it only accounted for 10 percent of the attack in age class 6 to 8. This suggests MPB attack may be waning. After attack, except in age class 6 to 8, residual stands were still pine dominated or pine leading. At best, residual stands are marginally stocked. There was at least 1500 sph of regeneration in all age classes. Pine was the dominant regeneration species in age class 1 and 2 and it contributed significantly in age class 3 and 4. In the older age classes, non pine conifers were the dominant regeneration. In the area sampled, older age class stands should remain stocked after the MPB epidemic has passed. These stands may be good candidates to be spared from harvest so they can contribute to the mid term timber supply. Residual age class 1 to 3 stands are of concern because they are essentially pure pine and the MPB beetle has just started attacking them. At minimum, there needs to be at least three management strategies: one for old age classes, one for the young, and another for intermediate age classes. Though difficult, many stands in the sub-zones sampled account for 35 percent of Prince George TSA timber harvesting land base can be managed to provide timber in the mid term.
Chris Hawkins and Patience Rakochy.
Hawkins, Chris D.B.. 2006. Stand to landscape level effects of the mountain pine beetle (MPB) outbreak in central British Columbia. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report. FIA2006MR262