Abstract
Within-stem variation of mechanical properties of Maritime pine timber (Pinus pinaster Ait.) as function of tree class quality and location of the specimens on the stem (percentage of stem height, distance to pith and orientation) is discussed. The results show a strong and consistent effect of the distance to pith on all mechanical properties studied. A trend for the decrease of mechanical properties along the stem (from butt to top) was detected probably due to the growing presence of juvenile wood caused by tree taper and vicinity to crown. Juvenile wood thus seems to play a decisive role on the within-stem variation of mechanical properties. A clear increase on bending strength (55%), modulus of elasticity parallel to grain (99%), compression strength parallel to grain (44%) and tension strength perpendicular to grain (27%) for distance to pith from 10% to 90% of the trunk radius was observed at all tree height levels studied. Orientation (north or south location on the stem) appears to be negligible.
Zusammenfassung
In der vorliegenden Arbeit werden Schwankungen mechanischer Eigenschaften im Stammholz von maritimer Kiefer (Pinus pinaster Ait.) als Funktion von Baumklassenqualität und Ort der Probenentnahme auf dem Stamm (Prozent der Stammhöhe, Entfernung zur Markröhre und Faserorientierung) diskutiert. Die Ergebnisse zeigen einen gleichbleibend starken Einfluss des Abstands zur Markröhre auf alle untersuchten mechanischen Eigenschaften. Festgestellt wurde eine Tendenz zur Abnahme der mechanischen Eigenschaften entlang des Stammes von unten nach oben, was vermutlich auf die Zunahme des Anteils von Juvenilholz bei gleichzeitiger Stammverjüngung in Richtung Baumkrone zurückzuführen ist. So scheint Juvenilholz eine entscheidende Rolle bei Schwankungen mechanischer Eigenschaften in Stammholz zu spielen. Eine klare Zunahme des Einflusses auf die Biegefestigkeit (55%), auf den E-Modul parallel zur Faser (99%), auf die Längsdruck - (44%) und Zugfestigkeit (27%) senkrecht zur Faser bei Entfernung zur Markröhre von 10–90% des Baumumfanges wurde auf allen Ebenen der Stammhöhe festgestellt. Die Faserrichtung (Nord- oder Südorientierung) scheint keine Rolle zu spielen.
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Machado, J.S., Cruz, H.P. Within stem variation of Maritime Pine timber mechanichal properties. Holz Roh Werkst 63, 154–159 (2005). https://doi.org/10.1007/s00107-004-0560-4
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DOI: https://doi.org/10.1007/s00107-004-0560-4