%0 Research article
%T Influence of pruning on wood characters in hybrid aspen
%A Rytter, Lars
%A Jansson, Gunnar
%D 2009
%J Silva Fennica
%V 43
%N 4
%R doi:10.14214/sf.189
%U https://silvafennica.fi/article/189
%X Fast-growing hybrid aspens (Populus tremula L. x P. tremuloides Michx.)  are currently of great interest in Sweden since they can produce biomass  at high rates and, at the same time, can be used to produce higher  value wood products. This study focuses on the effects of pruning hybrid  aspen to improve its wood quality. About 50% of the trees in the  experimental stand were pruned by removing twigs, at heights up to 4 m,  when they were 7–8 years old. Ten years later, 20 pruned and 20 unpruned  trees, representing four clones, were randomly selected. Ten knots or  twig/stem junctions, respectively, per tree were exposed for inspection  using a chain saw and examined. The results revealed that pruned trees  cicatrised the knots within about three years and thereafter produced  substantial amounts of faultless wood. In contrast, unpruned trees  (which had retained almost 80% of their twigs, often as dry twigs with  bark pockets) had produced small uneven amounts of quality wood. Removal  of twigs with acute angles and/or large diameters resulted in greater  colour defects and rot in annual rings outside the pruning position, but  the time of cicatrisation was not significantly affected. The results  show that pruning can be used to enhance the wood quality of hybrid  aspen over a short time period, and that pruning should be performed  early during the rotation period when branches are small, in order to  minimize discolouration and rot in the new annual rings.