Canadian Forest Service Publications
Proposed protocol for evaluating potential strength-reducing characteristics in lumber after a catastrophic event: Pilot application and next steps. 2009. Lum, C. Natural Resources Canada, Canadian Forest Service, Pacific Forestry Centre, Victoria, BC. Mountain Pine Beetle Working Paper 2009-01. 10 p.
Available from: Pacific Forestry Centre
Catalog ID: 29367
The production of lumber from mountain pine beetle (MPB)-attacked wood with the characteristic bluestain is not new. What is unprecedented is the scale of the attack and the volume of MPB-killed timber that needs to be processed in order to obtain the maximum possible value from the resource. When lumber is produced from dead standing timber, certain types of lumber strength-reducing characteristics appear in higher frequency. Depending on the biogeoclimatic conditions of the site, one might notice, for example, an increase in the occurrence of decay and/or shake in the ungraded lumber. Although much of the production is subsequently downgraded because of these characteristics, the lumber that remains in the grade still may have noticeably more pieces with these potential strength-reducing characteristics.
The industry has responded to the higher frequency of these characteristics by adopting new technology and by better preparing visual graders to deal with this resource. Nevertheless, the MPB epidemic has identified a need for an evaluation tool that helps the industry decide if the quality system needs to be adjusted to respond to the "sudden" appearance or increase in frequency of potential strength-reducing characteristics in a region.
The objective of this study is to develop a protocol for evaluating and responding to potential strength-reducing characteristics that develop in lumber from stands following a regional catastrophic event. This new protocol is intended to be distinct from the standardized lumber testing programs that are in place to support the development of structural design values.
Under this two-year project, a general protocol has been drafted and a limited pilot study was undertaken to demonstrate its efficacy by using shake in post-MPB lumber as an example. This protocol provides guidance on the identification of suitable characteristics for study, the design of an exploratory survey for assessing frequency of appearance, the approach for collecting samples for strength testing, the analysis of the test results, and, if necessary, the development of supplementary grading rules to respond to possible impacts to the lumber strength from these characteristics. The protocol will be presented to an industry Working Group charged with responding to issues arising from the MPB epidemic. It is anticipated that this protocol, when finalized, will form one of the basic Canadian tools on monitoring and assuring that published lumber design values continue to be applicable.