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 vol. 44 no. 2 article id 154. https://doi.org/10.14214/sf.154

Keywords: Pinus sylvestris; spiral grain angle; warp; sawn timber; breeding

Abstract | View details | Full text in PDF | Author Info

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.

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

article id 666, category Research article

Rolf Pape. (1999). Influence of thinning on spiral grain in Norway spruce grown on highly productive sites in southern Sweden. Silva Fennica vol. 33 no. 1 article id 666. https://doi.org/10.14214/sf.666

Keywords: Norway spruce; thinning; grain angle; ring width; growth rate; spiral grain

Abstract | View details | Full text in PDF | Author Info

Grain spirality was investigated in eight stands of Norway spruce (Picea abies (L.) Karst.) subjected to different thinning regimes. The dominating general pattern of spiral grain found in this study was typical for conifers, with a maximum of left-handed spirality close to the pith, which decreased towards the bark and sometimes changed to right-handed spiral grain in the outer growth rings. However, there was a large amount of between-tree variation in spiral grain. The effect of thinning on grain spirality was investigated by relating annual ring width to spiral grain, since thinning affects growth rate. A positive correlation between ring width and grain angle was found, but a considerable number of trees showed no or a negative correlation. A statistically significant effect of ring width was only found in five of the eight stands. Heavy thinnings, removing 60% of the basal area of a stand, considerably increased spiral grain, whereas the effects of light thinnings were inconsistent. These results support the findings of earlier studies indicating that spiral grain formation is under considerable genetic control, while its expression can be changed by silvicultural methods which affect growth rate.

Pape, Swedish University of Agricultural Sciences, Department of Forest Yield Research, P.O. Box 7061, S-750 07 Uppsala, Sweden E-mail: rolf.pape@sprod.slu.se

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