The elasticity and vertical distribution of stress within stems of Picea sitchensis.

Eight 22-year-old Picea sitchensis (Bong.) Carr. trees growing in a Scottish forest were bent using a winch and cable. The shapes of the bent stems were modeled using the structural theory of a cantilever beam, with non-uniform stem taper and large deflections taken into account. The Young's modulus of elasticity for the stems was estimated to be 2.0-6.4 GPa, which is lower than that reported for sawn green timber of this species, but similar to that for intact green stem sections. The longitudinal distribution of stress along the stems had a maximum at a height that was dependent on taper. Maximum stress occurred higher up in the more tapered stems.