UBC Theses and Dissertations
Juvenile - mature wood transition in second-growth coastal Douglas-fir Di Lucca, Carlos Mario
The transition from old-growth to second-growth British Columbia coastal Douglas-fir has resulted in reduction of log size and increased proportion of juvenile (core or crown-formed) wood. Determination of the zone of transition from juvenile to mature wood is critical to the definition of wood quality and timber value. Thirteen unpruned, two pruned second-growth, and two unpruned plantation-grown coastal Douglas-fir trees were sampled to analyze the hypothesis that the transition in relative density from juvenile to mature wood occurs at the base of the live crown. X-ray densftometric techniques were utilized to determine yearly pith to bark relative density data of five cross-sectional discs from each tree. Segmented linear regression techniques were utilized to estimate the juvenile - mature wood transition age from the data. The average number of growth increments from the pith at which juvenile - mature wood transition occurred on sections sampled at breast height, 20 percent and 40 percent of total height was 22.18. When the hypothesis was tested on unpruned trees, before and after harvest, the juvenile - mature wood transition occurred below the base of the live crown. When the hypothesis was tested on pruned trees, the transition occurred at the base of the live crown, which represented the upper limit of pruning height. This information may provide a greater insight into juvenile - mature wood transition. It will likely assist in the determination of wood quality and economic value of forest products manufactured from second-growth coastal Douglas-fir.
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