The potential of improving western hemlock pulp and paper quality. I. Genetic control and interrelationships of wood and fibre traits

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Abstract
This paper reports relationships between wood and fibre traits and investigates the potential for using genetic selection to improve traits that will increase both the yield and the value of the western hemlock (Tsuga heterophylla (Raf.) Sarg.) pulpwood resource. Strong family effects were present in the internal wood and fibre properties of relative wood density, average fibre length, and fibre coarseness. Heritability estimates for these traits ranged from 0.5 to 0.9. Heritability estimates for growth variables of height and diameter ranged from 0.15 to 0.2. Beside the moderate to high heritabilities for internal wood variables, coefficients of variation at the individual and family mean level ranged from 7.5 to 13% and from 4 to 6.5%, respectively. Correlations at an individual phenotypic and genetic level showed adverse correlations between growth rate and both relative wood density (negative correlation) and fibre coarseness (positive correlation). A significant negative phenotypic correlation between relative wood density and coarseness would appear to be due to the fact that both traits were strongly correlated to growth rate. The partial correlation controlling for diameter between coarseness and diameter was nonsignificant. Power analysis demonstrated that pulp and fibre traits could be assessed effectively using as few as six individuals per family.