-Wood stiffness varies enormously both within and between trees, so it is inevitable that low-grade solid wood products are produced from some trees. Accordingly, it would be highly desirable to segregate logs to ensure that only those logs with predominantly high stiffness wood are processed into structural lumber products. This study examined whether sound flight velocity (m s -1 ) could be used as a direct measure of wood stiffness to allow such segregation. Trees of radiata pine were measured before and after harvest with a non-destructive acoustic device (stress wave timer) to see if there was a relationship between sound wave velocity in either standing trees or logs and machine stress-grades of boards derived from those trees and logs. The speed of sound along logs was sufficiently closely correlated with wood stiffness to allow logs to be sorted into classes. A highly significant and positive relationship was found for acoustic measurements made in logs and a weaker, but still significant, relationship existed for acoustic measurements made in standing trees. Such segregation of logs according to wave velocity measured in the field may save a large sawmill between A$1-4m each year. Acoustic methods may also be used as an indirect tool for selection provided the heritability of the measurements is high enough and there is significant genetic correlation with genetic values for wood stiffness. From another experiment we have estimated the heritability of several acoustic measures and hope to be able to estimate genetic relationships with wood quality soon. modulus of elasticity / wood, acoustics / sound speed / selection Résumé -Classement des grumes de pin radiata selon le module d'élasticité par méthode acoustique. Les variations de module d'élasticité du bois, aussi bien inter-qu'intra-arbre peuvent être considérables. Il est alors inévitable de trouver des pièces de qualité mécanique médiocre en scierie. Il serait donc tout à fait souhaitable de pouvoir classer les grumes de telle sorte que seules celles qui pourront donner des sciages de qualité soient orientées pour la production de bois d'oeuvre. Cette étude analyse la possibilité d'utiliser la vitesse de propagation du son dans le bois comme estimateur du module d'élasticité permettant un tel classement. Plusieurs pins radiata ont été mesurés avant et après abattage par une méthode non destructive afin d'analyser la relation entre la vitesse du son mesurée dans l'arbre sur pied ou la grume d'une part, et le classement mécanique sur machine des planches issues de ces grumes d'autre part. La corrélation positive et très significative mesurée sur grume est suffisamment élevée pour permettre le classement de ces grumes. Cette corrélation est plus faible, mais reste significative pour les mesures effectuées sur pied. Un classement des grumes effectué de cette façon sur chantier permettrait à une scierie de grande taille d'économiser de 1 à 4 millions de dollars australiens chaque année. Les méthodes acoustiques pourraient aussi être utilisées c...

The effect of thinning on the relationship of wood quality traits measured on standing trees (dynamic modulus of elasticity (MOE) and outerwood density) and traits measured on logs or short clear specimens was determined using data collected from radiata pine ( Pinus radiata D. Don) trees growing in 22 unthinned and 16 thinned plots of harvest age trees in New South Wales, Australia. Stiffness showed a linear decrease along the stem. Trees growing on thinned sites were, on average, 3% lower in stiffness at each height in the stem. MOE measured on short clear specimens was moderately related to standing tree MOE (R2 = 0.62) and outerwood density (R2 = 0.56) but less well related to MOE of the adjacent log (R2 = 0.30). Standing tree MOE was a better predictor of whole stem MOE for the thinned sites (R2 = 0.60) than for the unthinned sites (R2 = 0.31). Stiffness and density appear to follow different patterns of variation and results for density may not be extrapolated to stiffness. Outerwood density was a very poor predictor of mean whole stem stiffness (R2 = 0.14). Overall, the acoustic tool, TreeTap, was a better predictor of whole stem stiffness than outerwood density, particularly for the thinned sites.

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