Deformations of boards from uneven-aged Norway spruce stands

Abstract

This study focused on wood distortion of boards sawn from Norway spruce (Picea abies (L.) Karst.) trees grown in uneven-aged stands. The stands were multi-aged with tree ages up to 170 years. In total, 60 trees were harvested from six stands that had been managed by single-tree selection for decades. A butt log and a top log were sawn from each tree, both 2.5 m long. Wood deformations were measured from boards dried to an average moisture content of 7–10% from the 2.5 m long boards. A linear mixed model was constructed to describe the variation in twist deformations in the boards after drying. According to the model analysis, twist increased with greater grain angle, greater average annual ring width and relative ring width difference, greater knot size and count, and the interaction of grain angle with the vertical log position along the stem. Greater distance of the board from the pith was associated with lesser twist. Contrary to expectations, proportion of compression wood and tree position in the stand diameter distribution were not correlated with twist. Pin knots, although their occurrence and size was minimal, had a high degree of correlation with twist. The occurrence and severity of twist remained approximately at the same level as in even-aged Norway spruce as observed in other studies.