Characteristics of the wood of young, fast-grown trees of Eucalyptus nitens with special reference to provenance variation.  R. J. McKimm.  August 1984.  26 pp. + App. (7 pp.). (unpubl.)

SUMMARY

This report describes a study of the variation in wood properties attributable to provenance of 8.5-year-old fast-grown Eucalyptus nitens Maiden (shining gum). Peripheral longitudinal strain, basic density, mechanical strength properties and treatability of the timber in dominant trees were measured. The results of a preliminary study of dimensional stability in sawn timber on seasoning of the same species, are also described.

Mean diameter, height and volume growth of the dominant trees sampled differed significantly between provenances. The frequency of dead branches was not related to provenance. Although no specific measurement was made of the incidence of knots, observations suggest that the frequency of knots in the material examined could present a problem in grading timber sawn for structural products. Sapwood comprised a high proportion of the timber volume in each of the sample trees.

A highly significant difference was found between peripheral longitudinal strain in the wood of one provenance (northern N.S.W., Mt Ebor) and the others. This property was not related to growth rate, and the values recorded, except for that provenance, were generally within the range reported for E. regnans F. Muell. (mountain ash) regrowth of 1939 origin. Basic density of the sapwood was generally significantly higher than that of the heartwood, but was not related to provenance. Other strength properties, such as moduli of elasticity and rupture, crushing strength and hardness, were influenced by provenance but only in either green or seasoned wood. Only compression strength perpendicular to the grain was significantly influenced by provenance in both green and dry wood.

Seasoned and unseasoned specimens of inner wood had significantly lower strength properties than outer-wood specimens. Strength properties were generally found to be lower than those for wood from mature trees of E. nitens, E. regnans and E. delegatensis R. T. Baker (alpine ash), yet comparable with those for Pinus radiata D. Don (radiata pine), indicating that sawn material should be suitable for structural purposes.

Preservative penetration into both inner and outer-wood specimens was readily achieved, and approximately doubled when the treatment pressure was raised from 400 to 1500 kPa. Increasing the treatment pressure above 1500 kPa did not increase any further the amount of preservative retained in the wood. Penetration of preservative was for the main part confined to the sapwood of outer-wood specimens and the juvenile wood near the pith of inner-wood specimens.

Twist, spring and bow in the sawn timber, off the saw and after reconditioning, were within the permissible limits prescribed in the Australian Standards.

Also published:

McKimm, R.J. (1985)  Characteristics of the wood of young, fast grown trees of Eucalyptus nitens Maiden with special reference to provenance variation.  I. Variations in growth, strain and density associated with provenance.  Aust. For. Res. 15 (2): 207-18.

McKimm, R.J. (1985)  Characteristics of the wood of young, fast grown trees of Eucalyptus nitens Maiden with special reference to provenance variation.  II. Strength, dimensional stability and preservation characteristics.  Aust. For. Res. 15 (2): 219-34.