Three-dimensional spiral grain pattern in five large Norway spruce stems

Abstract

GjerdrumThere 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, threedimensional 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.

Age and weather effects on between and within ring variations of number, width and coarseness of tracheids and radial growth of young Norway spruce

“…Considering the commercial importance of Norway spruce, it is little surprising that models addressing stem, wood and fibre properties and their variations within stems have been presented at different levels of detail, ranging from the stem shape and taper to specific fibre properties. Prominent examples are the models for external tree properties such as branchiness (Moberg 1999;Seifert and Pretzsch 2004;Seifert 2003;Hein et al 2007), models for spiral grain and inner defects such as resin pockets (Gjerdrum and Bernabei 2009;Seifert et al 2010), and the models from the joint works of Wilhelmsson et al (2002) on wood properties and Lundqvist et al (2002) on fibre properties, estimating property variations radially and longitudinally in stems of trees at different ages, latitudes and growth conditions, modelled from data on the same large set of trees from across Sweden. These models were developed for optimisation of wood use from an industrial perspective, based on data from pith to bark at different heights of trees ready for thinning or final cut, spanning ages from 30 to 150 years.…”

A multidimensional statistical model for wood data analysis, with density estimated from CT scanning data as an example

“…Gjerdum and Bernabei (2009) modeled grain angle in 3-D for Norway spruce (Picea abies (L.) Karst.) wood and stated that the interpretation of statistical analyses was limited by the lack of modeling of autocorrelation.…”

Deformations of boards from uneven-aged Norway spruce stands

“…Wood density and its variation, and annual ring width and its orientation, are closely related to the proportion of juvenile wood in uneven-aged trees (Piispanen et al 2014). Juvenility, its variation, ring curvature, knots, proportion of reaction wood and its distribution along the stem, and spiral grain angle are known to be correlated with the distortion of boards (Sandberg 2005;Bäckström and Johansson 2006;Gjerdrum and Bernabei 2009;Straže et al 2011). Juvenile wood (Sandberg 2005), microfibril angle and large knots are common causes for higher longitudinal shrinkage (Perstorper et al 2001), which together with growth ring curvature (Johansson et al 2001;Straže et al 2011) have been suggested as the main factors relating specifically to twist distortion.…”

“…Juvenile wood (Sandberg 2005), microfibril angle and large knots are common causes for higher longitudinal shrinkage (Perstorper et al 2001), which together with growth ring curvature (Johansson et al 2001;Straže et al 2011) have been suggested as the main factors relating specifically to twist distortion. Grain pattern, although highly variable from the pith to bark, is closely related to deformations of boards, especially twist (Forsberg 1999;Gjerdrum and Bernabei 2009). Structural elements, like knots and undulating pith, are also related to irregularities in the grain pattern.…”