UBC Theses and Dissertations
Influence of cambial ageing, initial spacing, stem taper and growth rate on the wood quality of three coastal conifers Fabris, Stéphanne
As the forest industry in British Columbia becomes increasingly dependent on second-growth timber for its raw material supply, the question of wood quality becomes more relevant. Accelerated growth in forest plantations, coupled with an earlier harvest, will lead to changes in the quality of the timber harvested. The influence of cambial aging, initial spacing, stem taper and growth rate was non-destructively evaluated on the wood quality characteristics of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii), western hemlock (Tsuga heterophylla (Raf.) Sarg.) and western redcedar (Thuja plicata Donn ex D. Don). The wood properties analysed included ring width, earlywood width, latewood width, latewood proportion, earlywood relative density, latewood relative density, whole-ring relative density, whole-ring tracheid length and microfibril angle. Juvenile wood development was determined based on whole-ring relative density trends from pith to bark. A highly significant cambial age effect was noted for practically each wood property considered. An identical pattern of development, regardless of spacing or taper class, was identified for Douglas-fir via latewood proportion and whole-ring relative density, and for western hemlock via latewood width, earlywood relative density, latewood relative density, whole-ring tracheid length and microfibril angle. No identical results were identified for western redcedar. An increasingly non-significant relationship evolved over time for Douglas-fir between growth rate and whole-ring relative density. A slight, but increasingly negative relationship unfolded for western hemlock. An increasingly stronger negative relationship developed for western redcedar. The Kajaani FS-200 Optical Fibre Analyser was found inadequate for measuring tracheid length variability on the basis of 12 mm increment cores. A gradual decrease in juvenile wood ring count was commonly identified with increasing height. Generally speaking for both Douglas-fir and western hemlock, the larger the volume of crown foliage relative to length of branch-free stem, the lower the passage from juvenile wood to mature wood below the base of the live crown. In the case of western redcedar, the larger the volume of crown foliage relative to length of branch-free stem, the higher the passage. The use of a variable exponent taper equation was explored for predicting juvenile core development.
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