CONTRIBUTION TO STUDY OF INTERNAL STRESSES IN WOOD OF EUCALYPTUS

Research was carried out to reduce internal stresses in E. camaldulensis. Altogether, 74 trees of the Circeo National Park were examined; 25 eucalypts were girdled, the cut affecting the entire sapwood, while the remaining trees were taken as controls. They were utilized at different periods after girdling, viz. after 5, 8 and 17 months. The investigations were carried out on butt-logs (up to a height of 3 m) of which diametral boards, 3 m long, were taken, having a thickness proportional to the mean breast height diameter of each tree. The measurements were taken of a total length of 100 in. by a tensodeformometer with an approximation of 0.0001″, determining, together with the length, also the deflection of all the outer strips gradually removed from the board in order to evaluate the strip unit contraction. As concerns board lengthening, the arithmetical difference was determined between the lengths taken before and after the cut. While for unit contractions-expressed by 8 d/l2-the values are given in in./sq.in., for unit lengthenings the variations are given in inches. The results obtained must be considered as positive: in fact, deformations were reduced, on the average, to 50 percent. These positive results are accompanied by others, of practical nature, all supporting the effectiveness of the method followed. Mention should be made, in fact, that in sawing logs from control trees diverse cracks occurred very often along the pith, separating diametrical boards almost completely, while no fissure was observed on boards from girdled trees. © 1969 Springer-Verlag.