%0 Research article
%T Three-dimensional spiral grain pattern in five large Norway spruce stems
%A Gjerdrum, Peder
%A Bernabei, Mauro
%D 2009
%J Silva Fennica
%V 43
%N 3
%R doi:10.14214/sf.200
%U https://silvafennica.fi/article/200
%X There is a great deal of interest involved in investigating and  understanding grain angle in trees. The objective of the study presented  in this paper has been to identify a joint, three-dimensional model for  grain angle in stems of Norway spruce (Picea abies (L.) Karst.) Five  large spruce trees were sampled. Transverse disks were extracted at  regular intervals along the stem, split through the pith with a blunt  knife, and observed for grain angle and cambial age along the north  radius, setting pith observation to zero angle. The overall finding  confirmed grain pattern congruent to distance from pith along the stem, a  pattern that varies from tree to tree. Models expressing distance from  the pith in cambial age performed slightly better than models in spatial  distance. Grain pattern changed slightly along the stem, and this  change was found to be consistent for the five stems: the left-handed  grain angle in the juvenile wood was more pronounced upwards in the  stem, and the angle changed faster towards right-handed spiralling. The  model did not account for grain variation related to knots, undulating  pith or other irregularities. Model residuals were normally distributed  and seemingly homogeneous for all trees and for all height levels. The  model is an extension of existing two-dimensional models for stem  cross-cuts. After verification in a wider sample, the results should be  applicable in tree and wood modelling.