Effect of Precommercial Thinning on Residual Sawmill Chip Kraft Pulping and Pulp Quality in Balsam fir

This study examined the effects of precommercial thinning (PCT) on kraft pulping and pulp properties of balsam fir [Abies balsamea (L.) Mill.]. Heavy precommercial thinning of balsam fir stands results in detrimental effects on the kraft pulping and pulp properties of the residual stems. It was found that at a stand density of 1,500 stems per hectare, sawmill residual chips obtained from the stems are more difficult to cook and exhibit a corresponding reduction in pulp yield with concomitant increased cooking chemical consumption. Shorter, finer fibers were observed, and the kappa 30 kraft pulps exhibited improved sheet tensile strength. These results indicate that balsam fir stems from heavily precommercially thinned stands contain a higher proportion of juvenile wood, although a contribution from compression wood cannot be completely ruled out