Variations in ring width density and tracheid morphology of tamarack wood (<i>Larix laricina</i>)

The tree genetic improvement programs focus on tree growth with little attention to wood quality despite determining the potential of wood for various applications. This study investigated the intra-ring and intra-tree variations of wood growth, density, tracheid length, and width of Larix laricina trees and estimated their quantitative genetic parameters of a 30-year-old progeny test using destructive and nondestructive samplings. The average ring density was 491 kg/m 3 . The proportion of latewood remains uniform and constant within the tree at about 24%. The tracheids were fine and long, averaging 25 µm in diameter and 2.23 mm in length for earlywood and 25 µm in diameter and 2.55 mm in length for latewood. The cambial age has a significant effect on almost all wood properties. A positive and significant phenotypic and genotypic correlation between density components was found for juvenile and mature wood. Tracheid morphological properties were positively correlated with each other and negatively correlated with wood density and growth components, except for earlywood density. Heritability estimates indicate that wood density components were under moderate to strong genetic control. These results showed that wood quality traits are important selection criteria for breeding programs to improve wood quality while maintaining a high growth rate.