Differences in intra-tree variation in spiral grain angle for radiata pine

Abstract

Background: Spiral grain angle (SGA) is an important factor affecting the distortion and utilisation of solid timber. Little research has investigated how SGA varies at a fine scale within trees and whether this fine-scale threedimensional variation is similar between genotypes. The objectives of this research were to (i) characterise threedimensional variation in SGA within stems and clones, and (ii) understand how intra-stem variation in SGA varies between genotypes.

Modelling spiral grain angle variation in New Zealand-grown radiata pine

“…The patterns of SGA predicted by the models generally confirms what has been described for radiata pine in the literature (e.g. Cown et al 1991b;Harris 1989;Lausberg et al 1995;Tian et al 1995;Watt et al 2013). In the radial direction, the models developed here showed that there is a predominantly linear decline in SGA with increasing ring number from the pith and the rate of decline decreases with increasing height up the stem.…”

“…Riddell et al 2012) now mean that it is possible to collect higher resolution data on the variation in SGA within a stem, particularly in the circumferential direction, which will enable a better understanding of the patterns of variation as well as providing better data for modelling this variation. Previous studies in radiata pine have noted that there is a large amount of tree-to-tree variation in the radial patterns of SGA (Cown et al 1991b;Watt et al 2013). The magnitude of this tree-to-tree variation is apparent in this study because when the random effects of site and tree were considered, the total amount of variation in SGA explained by the models almost doubled.…”

“…However, previous studies (e.g. Cown et al 1991b;Watt et al 2013) have reported near zero values of SGA near the pith followed by an increase to a maximum at ring 6-10 followed by a decline with increasing growth ring from the pith. This pattern was not predicted by the models, but this may be an artefact of the resolution of the data used to develop the models.…”

“…In the longitudinal direction a general trend of increasing SGA has been noted in the previous studies (Cown et al, 1991b). More quantitative information was provided in a recent study by Watt et al (2013) who found that SGA in 7-year-old radiata pine tree increased with height up the stem reaching a maximum at a height of 5 m. The additional amount of variation explained by the models when relative height terms were included is based on predicted values of relative height rather than measured values. These values have an error associated with them and it is recommended that tree height is measured in future studies investigating SGA, or other wood properties for that matter.…”

“…by Pape (1999). Although circumferential variation in grain angle has been noted on log exteriors and inside radiata pine stems (Cown et al 2010;Watt et al 2013), the degree of variability in within-stem and between-stem patterns and its potential importance in radiata pine is largely unknown. Despite all of the SGA measurements that have been made, good models to predict the withinand between-tree variation in radiata pine do not exist.…”