No abstract
The level of silvicultural investment and area of forest land managed in Canada is rising dramatically. Although this will increase growth rates and help maintain the present level of harvest, it may well result in a reduction in the quality of the resource. The present paper illustrates the risk of ignoring this potential problem through examples of experience in utilizing plantation-grown trees in various parts of the world. Relying on technology to solve all resource quality problems may not necessarily make economic sense. Canada's future must lie in the production of "value-added" products that require a high quality resource, permitting the greatest flexibility in conversion options. Information relating silvicultural treatments to end-product quality is at present inadequate. Large integrated studies addressing these questions and the economics of silvicultural investments in terms of end-product value must be initiated for species that will be managed intensively. With relatively long rotations, Canada cannot afford to create a resource that does not match its future marketing strategy.
This paper presents a discussion of the problems and opportunities in incorporating a consideration of wood quality into a tree improvement program. Attention is focused on the characteristic of wood density. The economic effect of a small (2%) change in western hemlock wood density as a raw material for pulp or lumber in Coastal British Columbia is predicted. Wood density as a selection criterion in a breeding program is of secondary importance to wood volume, but the potential loss in value and productivity through not considering wood density is simply too great to ignore. Resume(.'article presents une discussion sur les difficultes et les opport unites de prendre en consideration la qualite du bois dans les programmes d'amelioration des arbres. Uns attention particuliere est portee a la densite du bois. L'effet economique d'un faible changement de densite du bois (2%) sur la pruche occidentale utilisee dans I'industrie de la pate ou du sciage de la cote du Pacifique a ete evalue. Si la densite du bois comme critere de selection d'un programme d'hybridation est consideree comme secondaire par rapport au volume, elle n'est quand meme pas a negliger lorsqu'on considere les pertes potentielles en valeur et en productivity que son abaissement peut engendrer. Wood Quality and the Problem of Timber Supply
Stem eccentricity in second-growth western hemlock (Tsugaheterophylla (Raf.) Sarg.) from southern coastal British Columbia appears to be the rule rather than the exception. Although the difference was small, the average eccentricity ratios (ratios of minimum diameter inside bark (DIB) to maximum DIB) for two Lower Mainland sites were significantly larger than those of two Vancouver Island sites. The average eccentricity ratio of all 87 trees studied was 0.929, with a standard deviation of 0.0231. The angular rotation of the major axis of the stem cross section varied greatly, and was positively related to the average stem eccentricity ratio within 5-m log lengths for each stem. Average eccentricity of the whole stem was relatively independent of diameter at breast height (DBH), age, stem height, and eccentricity at breast height. It does not appear that a practical field technique could be devised for the rapid estimation of average stem eccentricity in western hemlock.
Consideration is given to the distribution of growth increment at 6 points up the stem of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) 5 years after fertilization. The fully stocked stand, near Port Alberni, B.C., was 49 years old with heights and diameters reaching 100 ft and 20 in. respectively when fertilized with 220 and 440 lb/acre of urea. No change of consequence occurred in tree form in the codominant and intermediate crown classes as a result of the volume response which was still evident, although greatly diminished, after 5 years. In dominant trees, however, cross-sectional area growth in the central third of the stem was less than the controls even though other parts of the bole showed a positive response which lasted until the 4th year. The net volume response was negligible. The estimation of volume response to fertilization in dominant trees from breast-height measurements should possibly be approached with caution.
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