Zur Holzqualität unterständiger Häher-Eichen in sächsischen Kiefernbeständen

2003

S. 128-131

20 Lit. Ang.

Unselbständiges Werk

200098347

The use of jay-sown European Oak (Quercus petraea, Q. robur) to reduce expenditures of the transformation of artificial pure-pine stands into mixed stands is mainly a question of the timber quality that can be expected. The compensation of unfavourable timber properties due to increment processes of the tree was analyzed and modelled in a joint study of the Saxonian Central Forestry Department (Landesforstpräsidium) and the Chair of Forest Utilization, Dresden University of Technology. A recently-developed method allowed the mapping of the form and the position of the trunk and the pith in three dimensions. Using this method, the analysis of a sample of 31 trees showed that a tree tries to compensate for bows with a higher radial increment on the concave side. The larger the bow, the significantly higher the reaction. Tree-ring analysis showed a decline in this compensation after an early maximum. This correlation can be fitted with the Hugershoff-function. In the group of bows stronger than 5 cm/m, a total compensation of 6 cm/m can be expected when a diameter of 40 cm is reached. European standards for average timber quality are likely to be met with a starting bow up to 10 cm/m. Compensation is quicker when annual ring width is larger. The process of self-pruning of the understory oaks was found to be insufficient. Almost none of the sample trees was likely to meet the criteria for knots of the new strict European standard CEN for average timber quality by the time they have reached harvesting diameter. Therefore, active (green) pruning is suggested. The costs are approximately 10 EUR per tree. Further investigation of this topic needs to be done. In comparison, a young understory oak, which has passed the main early mortal or devaluating risks, will occupy an area of 100m¬ by the time it reaches harvesting diameter. Just the planting of oak on this area costs 35 EUR. So there is promising evidence that pruning pays!