Variabilität der Faserneigung im Holz der Esche (Fraxinus excelsior L.) und Douglasie (Pseudotsuga menziesii (Mirb.) FRANCO)

The central aim of this project was the quantification and the analysis of the components of variation of the fibre angle in wood of Ash-as example for ringporous broadleaved species-and of Douglas fir—as example for coniferous species-as well as the review of the accuracy and representativity of a oftenly used method on log discs, which consists in the determination of the average of two diametral opposite values of fibre angle within one growth ring. The annual fibre angle was determined on 32 radii of six disc samples of Ash and Douglas fir with a specially designed protractor constructed at the Department of Forest Utilization of the University in Göttingen. The obtained results show a significant tangential variation of the fibre angle within one annual growth ring, which is at least as pronounced as the radial interannual variation, which is already well known from other investigations. In addition, small but significant differences were observed between the fibre angle values of earlywood and latewood of the same annual growth ring. It follows from these three observed variation components that this investigated method can be only used in limited cases for douglas fir and Ash. The observed overlapping of these variations is an important element of uncertainty for the data analysis, which makes more difficult the interpretation of causal relations between growth conditions, age etc. and fibre orientation in wood.