Canadian Forest Service Publications

Modeling the transition from juvenile to mature wood using modulus of elasticity in lodgepole pine. 2013. Wang, M.; Stewart, J.D. Western Journal of Applied Forestry 28(4):135-142.

Year: 2013

Issued by: Northern Forestry Centre

Catalog ID: 35291

Language: English

Availability: Order paper copy (free), PDF (request by e-mail)

Available from the Journal's Web site.
DOI: 10.5849/wjaf.12-026

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The transition of modulus of elasticity (MOE) values from juvenile to mature wood marks the change between variable, low-quality wood to wood that is stronger and more consistent. Knowing the proportion of mature wood in a log can lower processing costs and allow for higher-quality products. We measured MOE in breast height pith-to-bark samples from lodgepole pine (Pinus contorta) trees in six sites in Alberta and British Columbia, Canada. We assessed eight different two-segment regression models (a first linear, quadratic, exponential or power segment, and a second linear or constant segment) to determine the transition point from juvenile to mature wood based on MOE. All eight models provided useful and significant estimates of the transition point. For the first segment (juvenile phase), the quadratic form predicted the latest transition to mature wood, the exponential form predicted the earliest transition, and the linear and power forms were intermediate. Use of a linear form for the second segment (mature phase) provided only a minor improvement over use of a constant. There were significant differences in transition point based on MOE among some of the sites, and correlations between transition points and tree diameter or height were found at two of the six sites.

Plain Language Summary

Lodgepole pine is an economically important tree in Canada, used for both pulp and lumber production. However, the quality of the wood within logs is variable, with juvenile wood being of lower quality and mature wood being stronger and higher quality. Knowing the proportion of mature wood within lodgepole pine logs would help wood processors mill juvenile wood for low-quality lumber or biomass and mature wood for high-quality lumber or veneer. To determine this, the researchers used samples of lodgepole pines from six sites in Alberta and British Columbia. They used various mathematical models to discover which best determined the “transition point” — the age at which the wood within the log becomes mature — based on modulus of elasticity, a fibre characteristic related to wood strength. They found mathematical models that help predict where lodgepole pine wood is mature, but the “transition point” for trees varied from one site to another. They also found that tree diameter and height were related to the tree’s transition point at two of the sites, which would further assist in estimating the proportion of mature wood. These data are a first step in helping wood processors to make better use of logs, reducing waste and production costs.