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Doctoral thesis, 2010

Genetic improvement of shape stability in Norway spruce and Scots pine sawn timber

Hallingbäck, Henrik

Abstract

Poor shape stability of sawn softwood timber, causes substantial economic losses for sawmills and the building industry. Sawn timber twist is regarded to be the most severe deformation and has been shown to be controlled by intrinsic wood properties like wood shrinkage and spiral grain angle. The aim of the studies this thesis is based upon was to investigate the possibility to improve sawn timber shape stability, by genetic selection of genotypes of Norway spruce (Picea abies L. Karst.) and Scots pine (Pinus sylvestris L.) with a favourable spiral grain angle. Genetic parameters were estimated for the spiral grain angle in the mature wood of trees in four progeny trials (age 27–36 years) and two clonal trials (age 19 years) of Norway spruce. In addition, in a 36-year-old Scots pine progeny trial, the grain angle was measured and shape stability traits of the boards sawn from sampled trees were assessed. The estimates of genetic standard deviation (0.7°–0.9°) and heritability (0.29–0.42) in the mature wood of both species suggested that grain angle could be altered by genetic selection. The grain angle measured in single annual rings of Scots pine showed substantial phenotypic correlations (0.54–0.70) with the twist of small sawn timber dried to a 12% moisture content. As an example, twist could potentially be reduced by 0.3°–0.7° by selecting 20% of the parents displaying the lowest grain angle, thereby appreciably decreasing the percentage of excessively twisted boards. Grain angle under bark exhibited non-significant genetic correlations, close to zero, with growth traits, stem form, and branch traits in both species, and with pilodyn penetration in Norway spruce, suggesting that genetic selection for this trait would not generate any appreciable response in the other traits. The results of the studies imply that the grain angle measured under bark is utilisable in terms of genetic parameter estimation and for predicting the twist propensity of small sawn timber. This suggests that there is potential to improve sawn timber shape stability by genetic selection for a lower grain angle under bark and thus reducing the twist of sawn timber.

Keywords

picea abies; pinus sylvestris; forest trees; genetic variation; heritability; sawnwood; wood properties; wood defects

Published in

Acta Universitatis Agriculturae Sueciae
2010, number: 2010:22
ISBN: 9789157674999
Publisher: Department of Plant Biology and Forest Genetics, Swedish University of Agricultural Sciences

Authors' information

Swedish University of Agricultural Sciences, Department of Plant Biology

UKÄ Subject classification

Wood Science

URI (permanent link to this page)

https://res.slu.se/id/publ/28772