Seedling Characteristics and Kraft Pulping Properties of Young Douglas-Fir

A kraft pulping study has been made on young Douglas-fir trees thinned from an experimental plantation. The original purpose of the plantation was to establish whether properties of mature trees can be predicted by certain tree form characteristics of seedlings at age 2. These characteristics were, height (control and “super”) and branch count (high and low). Seedlings were selected from two nurseries (Corvallis and Salem) whose seed sources were geographically different. At the time of thinning, the control trees were on the average smaller in volume and shorter than the “super” trees, and the trees from the Salem nursery were shorter and smaller than their Corvallis counterparts. No significant difference was noted in the pulpability of the different trees, but certain pulp quality differences were noted. There were significant differences between the Corvallis and Salem trees in the bursting strengths and tensile strengths of their respective pulps, and this difference was considered due to probable differences in cell wall structure of the two classes of trees. There were no significant differences in tensile and bursting strengths between control and “super” pulps, By contrast, significant differences were found in these two properties between the high and low branch count trees. No significant differences were found for any pulp classification in the factors pulp yield, Kappa number, residual black liquor alkali, sheet density, stretch, tear, fold, or brightness. Compared to other Douglas fir draft pulps, these pulps on the average show higher sheet density, tensile, burst, and folding strengths, but lower tear strength. From a commercial standpoint, we postulate that these young Douglas fir trees produce pulp that would be quite suitable for linerboard, where bursting strength is the prime requirement. Similarly, it would, appear that seedlings may be selected for future pulping characteristics that would be valuable to the paper industry.

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