Defining the transition from earlywood to latewood in black spruce based on intra-ringwood density profiles from X-ray densitometry

Abstract

Defining the transition from earlywood to latewood in annual rings is an important task since the accuracy of measuring wood density and ring width components depends on the definition. Mork's index has long been used as an anatomical definition of the transition from earlywood to latewood. This definition is arbitrary and extremely difficult to apply to X-ray densitometry. For X-ray densitometry, a threshold density of between 0.40 to 0.55 g cm -3 , depending on species, has been chosen to differentiate between earlywood and latewood density, but this method has shortfall. Therefore, new methods need to be developed and integrated into the computational programs used to generate X-ray densitometry data. In this study, we presented a mathematical method. We modelled the intra-ring wood density profiles in 100 plantation-grown black spruce (Picea mariana (Mill.) B.S.P.) trees using high order polynomials. The correlation between the predicted and the measured densities is very high and highly significant. Based on this model, we define the transition from earlywood to latewood as the inflexion point. Results indicate that wood density at the earlywood-latewood transition point varies from juvenile to mature wood. This method could be easily integrated into any X-ray densitometry program and allows to compare individual rings in a consistent manner. transition / earlywood / latewood / X-ray densitometry / wood density / black spruce / modelling Rsum -Dfinition de la transition du bois initial au bois final chez l'pinette noire partir des profiles de densit intra cernes obtenus par densimtrie aux rayons X. La prcision de l'estimation des densits et des largeurs du bois initial et du bois final dans un cerne annuel dpend de la dfinition de la transition du bois initial au bois final. L'indice de Mork a longuement servi pour donner une dfinition anatomique cette transition. Cette dfinition est arbitraire et difficile appliquer en densimtrie aux rayons X. En gnral, un seuil de densit variant entre 0,40 0,55, dpendamment de l'essence, sert diffrencier le bois initial du bois final. Cette mthode a certaines limites et d'autres mthodes doivent tre dveloppes et intgres aux programmes de densimtrie aux rayons X. Nous avons utilis une approche mathmatique pour modliser les profiles de densit intra cernes dans 100 arbres d'pinette noire (Picea mariana (Mill.) B.S.P.). Le point d'inflexion de polynmes aux degrs levs a servi pour dfinir la transition du bois initial au bois final. Les corrlations entre les densits mesures et prdites sont leves et significatifs. La transition du bois initial au bois final varie entre le bois juvnile et le bois adulte. Cette mthode est facile intgrer dans les programmes de densimtrie aux rayons X et permet d'obtenir des comparaisons consistantes entre cernes annuels. transition / bois initial / bois final / densimtrie aux rayons X / densit du bois / pinette noire / modlisation