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Regional, Site, and Tree Variations of Wood Density and Growth in Thuja occidentalis L. in the Quebec Forest

Thuja occidentalis L. wood is desirabl, e for wooden structures that require wood density uniformity. Wood density is a wood quality indicator related to numerous morphological, mechanical, physiological, and ecological properties. This study aimed to investigate the regional, site, and tree-to-tree variations of T. occidentalis wood density and growth components through the analysis of X-ray densitometer data. A total of 287 trees were randomly sampled from 11 sites in the Abitibi-Témiscamingue regions in Québec, Canada. The average ring density at breast height was 356 kg m−3, with a small difference between earlywood and latewood (167 kg m−3), indicating a relatively uniform wood. Ring density and width varied significantly between the Abitibi and the Témiscamingue regions, mainly in the juvenile wood. Trees from the Abitibi region showed higher ring density than those in the Témiscamingue region. In contrast, the ring width was higher in the Témiscamingue region. Site, tree, and cambial age significantly (p < 0.001) affected wood density and growth components. However, the largest variation is due to the tree-to-tree variation, accounting for about 15%–31% of the total variation. Compared to ring widths, ring density components showed a considerably smaller tree-to-tree variation and higher variation (7.1%) with cambial age than ring widths (0.6%). Ring width correlated positively and significantly (p < 0.001) with average temperature and annual precipitation, while ring density correlated negatively and significantly (p < 0.001) with average temperature and annual precipitation.