QUALITY OF TIMBER PRODUCTS FROM NORWAY SPRUCE

Strength and stiffness together with some properties characterizing th e stand and the growth of trees were studied. Specimens (45 x 70 x 290 0 mm(3)) were cut from different radial and longitudinal positions, fr om fast-grown trees from two stands in southern Sweden. These trees ha d relatively large annual rings (4-6 mm) and were not representative o f Norway spruce in Sweden but are an example of the intensively-manage d stands which will probably constitute a substantial part of the raw material supply in the future. The results indicate that the mean valu es for strength and stiffness were lowest for the core studs and incre ased further away from the pith. This radial variation in strength and stiffness appears to be associated with the variation in ring width. Density alone, on the other hand, does not explain the radial variatio n but should be used together with either ring width or knot area rati o to explain the stiffness and strength respectively. The increase in the strength and stiffness of the core studs from the butt logs to the top logs was significant. Density alone was found to be the best vari able to explain the longitudinal variation between the butt logs and t he top logs. The heartwood formation in the butt log juvenile core app eared not to have a positive effect on strength and stiffness. The occ urrence of compression wood, the magnitude of grain angle and the marg in knot area ratio had only a minor effect on strength and stiffness.