Silva Fennica : regular issues : 44(2) : sa442275.htm

Henrik R. Hallingbäck, Gunnar Jansson, Björn Hannrup & Anders Fries. 2010.

Which annual rings to assess grain angles in breeding of Scots pine for improved shape stability of sawn timber?

Silva Fennica 44(2): 275–288

The shape stability properties of sawn timber could be improved by breeding or grading Scots pine (Pinus sylvestris L.) for reduced grain angles. Currently, only grain angle assessments performed in single annual rings can be considered feasible in forest breeding programmes. The relevance of such methods in assessing shape stability traits was evaluated by taking grain angle measurements beneath the bark in a 36-year-old Scots pine progeny trial. Several grain angle measurements from stem discs were also taken from a sample of 162 trees. Phenotypic correlations were estimated between grain angle and the bow, crook and twist developed in 316 sawn and dried boards. All single annual ring assessments, including measurements taken directly under the bark, were significantly correlated with twist. The highest correlations (0.60–0.70) were observed in annual rings numbered 8–20 and at distances of 30–70 mm from the pith, indicating those parts of logs where grain angles have the largest impact on twist. These results suggests, that grain angles measured beneath the bark are relevant to the twist of sawn small timber, and that any single annual ring could be chosen for the assessment, provided that the tree diameter is within the 60–140 mm range. No appreciable correlations were observed between grain angles and either crook or bow.

Keywords
spiral grain angle, warp, sawn timber, breeding, Pinus sylvestris

Addresses
Hallingbäck, Dept of Plant Biology and Forest Genetics, Swedish University of Agricultural Sciences, Uppsala, Sweden; Jansson and Hannrup, The Forestry Research Institute of Sweden, Uppsala, Sweden; Fries, Dept of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, Umeå, Sweden. E-mail henrik.hallingback@vbsg.slu.se

Received 16 December 2009 Revised 8 March 2010 Accepted 7 April 2010
ISSN 0037-5330

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