%0 Research article
%T Which annual rings to assess grain angles in breeding of Scots pine for improved shape stability of sawn timber?
%A Hallingbäck, Henrik R.
%A Jansson, Gunnar
%A Hannrup, Björn
%A Fries, Anders
%D 2010
%J Silva Fennica
%V 44
%N 2
%R doi:10.14214/sf.154
%U https://silvafennica.fi/article/154
%X 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.