Clonal and environmental variation of structural timbers of Eucalyptus for growth, density, and dynamic properties

Abstract

The main objective of Eucalyptus breeding programs for the pulp and paper industry is to produce varieties of treeswith high levels of cellulose with the least possible amount of lignin. However, trees with these characteristics can be a major problemin the field, because of their fragility that makes them susceptible to breaking. The aim of this study was to investigate the clonal andenvironmental variation of the growth, wood density, and dynamic properties on large pieces of Eucalyptus wood by means ofresonance technique. Here, we demonstrated that no other non-destructive technique is able to characterize the mechanical propertiesof wood so simply and rapidly at such low cost. The resonance technique provided a large, accurate data set of the key mechanicaltraits (such as the Young, the shear modulus and the loss tangent) of the wood even in lumber containing knots, small cracks and alsoslightly damaged areas. There were significant differences between clones and sites for height and circumference, and density of thetrees. Using the dynamic elastic estimates, significant differences were detected between clones for all traits; however, no significantdifferences between sites were detected for dynamic modulus of elasticity. There were significant effect of interaction clone x site forcircumference, height, density and shear modulus. These findings can be useful for screenings, classifications, or preliminary selectionsin breeding programs of Eucalyptus.