Moeglichkeiten zur Erweiterung des waldbaulichen Einflusses auf die Holzqualitaet der Douglasie

1997

S. 555-563

39 Lit. Ang.

Unselbständiges Werk

200039696

Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) has been planted in Germany since more than 100 years. It showsa superior growth compared to indigenious coniferous species, and is today the most important foreign species in Germany, covering more than 1,5% of the total forest area. Wood quality of german Douglas fir varies significantly according to site conditions and silvicultural treatment. On better sites, a relatively high proportion of juvenile wood, low density, wide growth rings and big branches are typical negative features for young Douglas fir stands. There have been several studies on the influence of initial spacing and thinning intensity on these woodn quality parameters. The results show, that an intensive competition between trees within the first 20 years can limit these negative effects, but one consequence is the reduction of the living crown to an extent, which may cause instability and increment losses in the future. This study shows the effect of an oak shelter during the first approx. 20 years on the quality of Douglas fir. Two neighbouring stands with a similar degree of shelter, but different initial spacing and thinning regimes were studied. The results show that even with a wide spacing the effect of the shelter can limit the negative implication of a vigorous growth in the youth, resulting in a more even distribution of ring width and density over the cross section of the stem. In the meantime the trees conserve a longer living crown which shows normal or even smaller branch diameters. Therefore a shelter of an adequate density may have a positive influence on the wood quality of young Douglas fir stands. To avoid sudden changes in the wood structure the removal of the shelter should not be executed at once, but step by step, beginning at the age of approx. 20-30 years.