Young's modulus of sections of living branches and tree trunks.

Young's modulus along the grain (elasticity, E) was measured on 10 sections of branches and three tree trunks, with bark, of Picea sitchensis (Bong.) Carr., Pinus contorta Dougl. ex Loud., Larix decidua Mill. and Betula pendula Roth. syn. verrucosa Ehrh. The sections were simply supported and corrections were made for taper and deflection due to shear. The E values for trunks were at the lower end of the range reported for green timber (2.4-7.5 GPa), and those for branches were still lower (0.7-4.6 GPa). Values of E for branches decreased with decrease in specific gravity, which corresponded with an increase in percentage water content. When E values were calculated using underbark diameters they fell more closely within the range reported for green timber.