Relationships between the intra-ring wood density assessed by X-ray densitometry and optical anatomical measurements in conifers. Consequences for the cell wall apparent density determination

Abstract

-The objective of this work is to compare anatomical measurements to wood density variations within annual rings of three major softwood species, Norway spruce, Scots Pine and Silver Fir. The six selected annual rings were sampled within a database of thousand microdensitometric profiles measured on wood samples collected in Finland and France. Each of the six studied annual rings represents one average profile of wood density for a given age class and age ring width. The dimensions of the tracheids are performed in the radial-tangential plane by using two different planimetric methods. The wood density profile within each ring is calculated simply by the mean of the tracheid dimensions and by using a constant value for the cell wall density. We have verified that the knowledge of the (i) tracheid geometry and (ii) the usually admitted value of the cell wall density allows us to calculate intra ring wood density profiles which are similar to the X-rays wood density profiles in terms of variations but very different in average. Thus it appears necessary to calibrate by using an apparent cell wall density varying inside the rings and being far weaker than the effective cell wall density of 1460 kg/m³ as it is usually admitted in the literature.wood density / wood anatomy / Picea abies / Pinus silvestris / Abies alba Résumé -Variations intra-cerne de densité du bois et mesures optiques des caractéristiques anatomiques de résineux. Conséquences pour la détermination de la densité apparente de paroi. L'objectif de ce travail est comparer des mesures anatomiques à des mesures de variations de densité du bois à l'intérieur de cernes annuels pour trois essences résineuses importantes, l'épicéa commun, le sapin pectiné et le pin sylvestre. Les cernes sélectionnés sont choisis dans un échantillon de plusieurs milliers de cernes prélevés dans des arbres en France et en Finlande. Chaque cerne étudié représente pour une essence le profil moyen de densité d'une classe d'âge compté depuis la moelle et d'une classe de largeur de cerne. Les caractéristiques géométriques des trachéides sont mesurées par deux méthodes planimétriques différentes dans le plan radial-tangentiel. Le profil de densité du bois est calculé simplement à partir des dimensions des trachéides et de la densité de la matière ligneuse. Pour que le profil calculé de densité du bois corresponde au profil obtenu par microdensitométrie nous avons montré qu'il est nécessaire faire varier le facteur de calibration, appelé densité apparente de la paroi cellulaire, à l'intérieur des cernes avec des valeurs bien plus faibles que 1460 kg/m³, la valeur habituellement utilisée dans la littérature. densité du bois / anatomie / Picea abies / Pinus silvestris / Abies alba

Wood density within Norway spruce stems

“…Decoux et al (2004) have reported that WD exhibits maximum variance within individual annual rings, ranging from ca. 300 to 1000 kg m -3 .…”

“…300 kg m -3 in earlywood to ca. 1000 kg m -3 in latewood (Olesen 1982, Mäkinen et al 2002b, Decoux et al 2004). The increase in WD from early-to latewood is mainly due to anatomical changes in tracheids (Kellogg andWangaard 1969, Skaar 1988).…”

Wood density and fiber dimensions of Gmelina arborea in fast growth trees in Costa Rica: relation to the growth rate

“…This variation is produced because of the differences in tracheid formation of early and latewood in softwood species (Decoux et al, 2004). In contrast with the hardwoods, the variation depends on the amount or proportion of different cell types and spatial arrangements (Guilley et al, 2003).…”

Variação da anatomia e da densidade básica da madeira de Gmelina arborea (Roxb.), em diferentes condições de clima e de manejo na Costa Rica

“…A densidade da madeira das espécies florestais é, reconhecidamente, a propriedade mais analisada nos laboratórios de tecnologia da madeira e de produtos florestais, pelas relações com as demais propriedades e utilização da madeira (Decoux et al, 2004), bem como na determinação da biomassa e incorporação do carbono pelo tronco das árvores e na caracterização dos anéis de crescimento (Guilley et al, 2004e Sckinker et al, 2003.…”

“…As variações da densidade da madeira de um anel de crescimento ou de uma seção transversal de amostra de madeira têm forte influência na qualidade de madeira (Echols, 1973) sendo mais importantes quando associadas às características anatômicas (Decoux et al, 2004).…”