%0 Research article
%T Influence of thinning on spiral grain in Norway spruce grown on highly productive sites in southern Sweden
%A Pape, Rolf
%D 1999
%J Silva Fennica
%V 33
%N 1
%R doi:10.14214/sf.666
%U https://silvafennica.fi/article/666
%X 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.