Rapid prediction of wood stiffness from microfibril angle and density.

Wood quality is rapidly becoming a major consideration in tree improvement programs. Rapid, cost-effective methods will be required to cope with the large numbers of samples (increment cores) generated by such programs. Wood stiffness, or longitudinal modulus of elasticity (EL) is one ofthe most important wood properties for solid timber applications and this paper describes a rapid method for predicting EL from measurements of density and microfibril angle (MFA). Very strong linear relationships have been found between E L , measured by a sonic resonance technique, and various combinations of wood density and MFA for 104 clearwood samples of Eucalyptus delegatensis R.T. Baker. Average MFA of each sample was measured in less than 1 minute by high-speed x-ray scanning diffractometry on SilviScan-2, a prototype automated wood microstructure analyzer. Density was measured gravimetrically. A small strip cut from one end of each sample was used for MFA analysis. In this study, density variation alone accounted for 70 percent of the variation in E L , while MFA alone accounted for 86 percent. Together, MFA and density accounted for 96 percent of the variation in E L . The results of this study indicate that density, MFA, and E L could be included in tree improvement programs using instruments based on SilviScan technology.