Effects of in-forest sorting of Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) on wood and fibre properties
1997
Duchesne, I. | Wilhelmsson, L. | Spangberg, K.
Logs from a mature stand of Picea abies (L.) Karst. and Pinus sylvestris L. were sorted into five pulpwood assortments to achieve better-defined raw material aimed at different fibre products. The sorting criteria were tree species, tree class, and log type. Differences in wood properties between species were moderate when equivalent log types were compared. Mean annual ring width and moisture content varied most between tree classes. Sorting based on log type resulted in the greatest differences in basic density, juvenile wood content, and heartwood content. Unbeaten kraft pulp from spruce assortments had weighted fibre length means of 3.1 down to 2.7 mm, while pine assortments had lengths between 2.7 and 2.5 mm. The largest percentage differences between the assortments were 6.3-14.8% for six strength indices. The differences in sheet densities and porosity were 5.0 and 50.4%, respectively. Differences in sheet properties were generally greater between log types than between species. Top logs exhibited the highest sheet densities, while middle logs showed slightly higher values for most strength properties. Spruce assortments tended to give better strength properties than pine, while middle logs of pine gave the highest porosity. By in-forest sorting, some concentration effects of fibres were achieved.
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