Untersuchungen über die Holzeigenschaften von Douglasien aus linksrheinischen Anbaugebieten

Abstract

The wood-properties of Douglas firs grown on various sites and under different growth conditions on the west-side of the Rhein in the districts Trier and Koblenz (mostly in the Eifel- and Hunsruck-hills) were investigated. Some of the test-trees were grown in pure stands, some in mixed stands between broadleaved species or spruces. Investigations comprehended year ring analysis, percentage of summerwood, thickness of branches, hardness, length of tracheids and wood density (based on volume when green and weight when ovendry). From several stems grown on a good site also the strength properties of wood were tested. For production of timber of high specific gravity and useful for deals and veneer an early limitation of diameter growth is desirable, however on better sites with abundant soil moisture supply is difficult to obtain. The best wood quality was found in densely stocked pure stands, while Douglas firs mixed in wide distance with broad-leaved species were rapidly grown, developed very big crowns with thick branches, conical trunks and broad annual rings. In the examined stands percentage of summer-wood was rather high. The average specific gravity value corresponded exactly with american second-growth stands of coast type. Test-trees from a fully stocked stand showed excellent stress properties, especially high values of bending strength, modulus of elasticity and shock resistance. The quality of the converted lumber cut from test-trees will be discussed in a following essay.