In the near future, new forests have to be cultivated on marginal agricultural lands to increase the amount of wood as a raw material for furniture, construction and for energy, and to stabilise the climate. Due to the existing climatic and site conditions, oak is planned to cover up to 25% of the forest area of northern regions of Germany.
Traditional silvicultural concepts prefer a high stocking density of oak by planting and thinning measures. This conservative treatment results in favourable properties of the oak wood (e.g. narrow rings), but causes high production time and costs.
To reduce these costs, it could be useful to accelerate diameter growth by decreasing the stocking density, but the consequences for the relevant technological wood properties have to be examined.
To do this, 2 x 15 trees were taken each from two neighbouring stands of English oak of the "Kottenforst". Both stands have the same age (90 years), but have been established and thinned in a different way: the "Heister" stand as a triangle planting 5 x 5 m, resulting in a stocking density of 170 trees per hectare today, the "Saat" stand as a seed with 500 kg acorns per hectare with the consequence of 340 trees per hectare at present. These stems have been selected randomly, cut into logs and sawn into 32 mm boards. Both the round wood and the timber quality of the two stands were analysed and compared by German standards and classification rules.
The results show that dimension (diameter at breast height) and quality of the round wood of the stand "Heister" exceed those of the stand "Saat" significantly, which results in a 7% higher output of sawn timber. The quality of the boards is even better in some cases, because the faster growth results in a better healing over of the knots. Ring width is slightly bigger (2.51 mm instead of 2.06 mm), but remains still within an acceptable range.
Key words: English oak, silvicultural treatment, round wood quality, timber quality.
Correspondence: Stefan Peters, Institute of Forest Utilization, University of Göttingen, Büsgenweg 4, D-37077 Göttingen, Germany