Genetic relationships between wood quality traits and diameter growth of juvenile core wood in Sitka spruce

The trend towards shorter rotations in planted conifer stands has resulted in a reduction in the proportion of mature wood relative to juvenile core wood, raising concerns that the mechanical performance of sawn battens will be affected. The potential to improve the wood quality of the juvenile core of Sitka spruce (Picea sitchensis (Bong.) Carriere) without compromising growth rate was investigated. Rapid and inexpensive indirect methods of assessing wood properties on standing trees using a Pilodyn gun and acoustic velocity were compared with direct measurements made on wood samples cut from the juvenile core. Strong genetic correlations were observed between Pilodyn gun values and direct measures of density (-0.76) and between the square of acoustic velocity and modulus of elasticity (0.73). The genetic correlation between the square of acoustic velocity and microfibril angle was also strong (-0.84). These results suggest that indirect assessments of wood properties within juvenile core wood are sufficiently reliable for these techniques to be used in the Sitka spruce breeding programme. Although a strong negative genetic correlation between diameter at breast height and density was noted (-0.79), sufficient variation exists within the breeding population to select families with both good growth rate and high modulus of elasticity wood. Resume: La tendance a raccourcir la periode rotation dans les plantations de coniferes a entra?ne une reduction de la proportion de bois de caeur mature relativement au bois de caeur juvenile. Cette situation fait craindre que la performance mecanique des tasseaux scies soit affectee. La possibilite d'ameliorer la qualite du bois de caeur juvenile de l'epicea de Sitka (Picea sitchensis (Bong.) Carriere), sans compromettre le taux de croissance, a ete etudiee. Des methodes indirectes, rapides et peu couteuses, pour evaluer les proprietes du bois dans les arbres sur pied a l'aide du pilodyn et de la vitesse sonique ont ete comparees a des mesures directes sur des echantillons de bois de caeur juvenile. D'etroites correlations genetiques ont ete observees entre les valeurs du pilodyn et les mesures directes de densite (-0,76) et entre la vitesse sonique au carre et le module d'elasticite 0,73). La correlation genetique entre la vitesse sonique au carre et l'angle des microfibrilles etait egalement etroite (-0,84). Ces resultats indiquent que l'evaluation indirecte des proprietes du bois dans le bois de caeur juvenile est suffisamment fiable pour que ces techniques soient utilisees dans le programme d'amelioration de l'epicea de Sitka. Bien qu'une etroite correlation genetique negative (-0,79) ait ete notee entre le diametre a hauteur de poitrine et la densite, il existe suffisamment de variation dans la population en selection pour selectionner des descendances qui ont un bon taux de croissance et dont le bois a un module d'elasticite eleve. [Traduit par la Redaction]
Introduction There are 700 000 ha of Sitka spruce (Picea sitchensis (Bong.) Carriere) 'plantation' forest in Britain and around 32 million Sitka spruce trees are planted annually, representing a major [...]