Spiral grain in clonal trial with Sitka spruce
1998
Hansen, J.K. | Roulund, H.
Grain angles to the left in seven clones of Sitka spruce (Picea sitchensis (Bong.) Carr.) decreased from the pith and outwards and with height. Effects of compression wood and compass directions were nonsignificant. Clones differed significantly but interacted with height levels, ring numbers, compass direction, and compression wood. However, the interaction with compression wood was small. Furthermore, some interaction with compass direction could possibly be attributed to eccentric stems and stem axis choice. The repeatability was 72% for averages of ramets measured in five height levels and most rings from the pith. The mean spiral grain was 2.2 degrees, and the phenotypic standard deviation between averages of ramets was 1.07 degrees. Genetic gains of 1 degree from phenotypic selections based on several measurements were suggested using these values. Variations between ramets and residual variances accounted for most of the variation. Thus, as many ramets as possible should be sampled to obtain the best estimates of mean clonal levels. Clone interactions with height levels and ring numbers from the pith were less important. This was also explained by correlations of 0.83-0.98 among clone averages at 1.3 m for single rings and overall clone means. Only significant effects ring widths were present within clones.
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