Intra-Ring Variations and Interrelationships for Selected Wood Anatomical and Physical Properties of Thuja Occidentalis L.

Intra-ring variation in wood density and tracheid anatomical properties and wood property interrelationships were investigated in Thuja occidentalis L. Samples were taken from three stands in Abitibi-Temiscamingue, Quebec, Canada. The structure of T. occidentalis wood is simple, homogeneous and uniform, which is desirable for wooden structures that require wood uniformity. From early- to latewood, cell and lumen diameter decreased, while cell wall thickness increased. These changes led to an increase of the cell wall proportion. Wood ring density and width interrelationships were weaker in mature wood compared to juvenile wood. Earlywood density is the more important in determining mature wood density than latewood density and proportion. Earlywood density explains 92% and 89% of the variation in juvenile and mature wood density, respectively. The negative relationship between ring density and width, although significant, was low and tends to weaken with increasing tree age, thus providing the opportunity for silvicultural practices to improve both growth and wood density. Ring width was positively and strongly correlated to early- and latewood width, but negatively correlated to tracheid length and latewood proportion. Accordingly, increases in ring width produce smaller tracheids and wider earlywood without a corresponding increase in latewood. Practical implications of the results are discussed.