This report examines the utility of using trembling aspen, white spruce, black spruce, lodgepole pine and jack pine in typical woodworking processes. The following three processes were considered: machining (including fastener withdrawal), laminating and finishing.
One hundred and eight white spruce (Picea glauca (Moench.) Voss) trees were systematically sampled by 30, 40 and 50 cm diameter-at-breast height (DBH) classes from three natural stands in Alberta located near Grande Prairie, Hinton and Whitecourt. Mean ages of the tree samples were 102, 128 and 100 years respectively. Based on sample trees, site indices at breast-height age 50 were 17.9, 19.7, and 20.0 respectively.
Wood basic relative density at breast height was determined for each sample tree by X-ray densitometry of increment cores. Mean relative density values for the 30, 40 and 50 cm DBH classes for the three samples combined were 0.38, 0.36 and 0.33 respectively compared to the species average of 0.354. ANOVA of basic relative density on DBH and stand (R2= 0.43) revealed that differences in DBH class (rate-of-growth) were significant (p = .0001). Differences in mean density between stands were not significant with values of 0.36, 0.36 and 0.35. Considered within each stand, wood density declined significantly (a = 0.05) as diameter class increased with the exception of the 30 and 40 cm classes at Grande Prairie. Pith-to-bark density trends were inversely related to ring width trends, consistent with expectations for white spruce.
Although generally somewhat higher, density trends coincided with those obtained from white spruce trees sampled similarly from three stands in northeastern British Columbia. In that study, trends in breast-height wood density were reflected in similar and more significant trends in bending modulus of rupture (MOR) and modulus of elasticity (MOE), MOE in compression, and ultimate compression strength (UCS) of small clear specimens.
The combined results of both studies demonstrate robustly that for stands of similar age and site index, wood density and related structural wood properties of white spruce are influenced primarily by rate-of-growth. Consistent results obtained in both mixedwood and conifer dominated stands are a further indication of robustness. Spurts in growth rate that occurred in two of the six samples corresponded to reductions in wood density. White spruce wood from natural stands is valued for its high strength to weight ratio. The implications of consistently lower wood density related to the most rapid rate-of-growth should be considered in decisions regarding the planting, spacing and thinning of future white spruce forests.