DRYING PROPERTIES AND VISUAL GRADING OF JUVENILE WOOD FROM FAST GROWN PICEA-ABIES AND PICEA-SITCHENSIS

Investigations concerning the drying properties (twist, longitudinal shrinkage, bow and spring) are made on boards from four young Norway spruce (Picea abies) and Sitka spruce (Picea sitchensis) stands grown on fertile soils. Initial spacing has been up to 2.5 x 3 m and thinning intensity has been heavy. Small, average and large trees from each stand were sampled, in total 78 trees sawn into 214 boards. The boards consist mainly of wide-ringed juvenile wood. Norway spruce and Sitka spruce of this material show only small differences in drying properties and they are accordingly analysed together. The boards are prone to severe twisting causing low-grade boards and a high percentage of rejection when visually graded. The twist is induced by spiral grain and is most pronounced in small-dimension boards sawn near the pith. Methods for reducing twist are discussed. Longitudinal shrinkage does not give problems for the use of the boards. Bow and spring give problems only for part of the boards, namely the very small dimensions from near the pith.