Solid-Wood Properties of Plantation-Grown Eucalyptus globulus: Their Variation, Effect and Evaluation

摘要

This paper reports the main findings of a comprehensive study of solid-wood properties of plantation-grown Eucalyptus globulus. Fifty-nine 10-year-old trees were sampled from three provenances grown at two separate sites in South Australia. The butt logs were back-sawn to produce 40 x 100 x 3600 mm boards. One full-diameter billet was removed from each tree and small clear specimens prepared. Several, key solid-wood properties were measured including growth strain, shrinkages, collapse, density, microfibril angle (MFA) and cellulose crystallite width (W_(cryst)). Between-site and between-provenance differences in these properties were investigated and their interrelationships examined. Knots and pith were primary grade-limiting defects, mainly because the trees were grown as pulp logs and harvested at 10 years of age. There were significant differences in mean growth strain between sites and provenances and among individual trees. King Island provenance had the lowest growth strain (710 x 10~(-6))and the least between-site and among-tree variation. Average growth strain and tree diameter at breast height in combination accounted for 42% of the variation in the percentage of excessively distorted boards. Highly significant between-site differencesin density, radial and tangential collapse, and total tangential shrinkage were observed. However, between-provenance differences in these four properties were insignificant. Total tangential shrinkage was found to be the best single predictor for tangential collapse (R~2= 0.896) and for total cross-sectional shrinkage (R~2 = 0.924} in wood blocks. These strong relationships hold for individual measurements as well as for tree means, and are not affected by positions along the radius. MFA and W_(cryst)were significantly correlated with several shrinkage properties. Density, MFA and W_(cryst) accounted for only small to modest amount of variation in shrinkage and collapse in either radial or tangential direction. Tangential collapse in wood blocks showed a high potential for identifying trees that developed internal checks during drying.