Variation of wood density and shrinkage in European aspen (Populus tremula)

The aim of this study was to investigate the variation in wood density and shrinkage within and between aspen stems. The studied material consists of 10 aspen (Populus tremula L.) stems. The stems were randomly selected from three pure aspen stands with similar diameters at breast height and with similar tree heights. The samples for measuring the wood density and shrinkage were taken at stump height and from the heights of 3, 6, 9, 12 and 15 meters. The results showed that wood density of European aspen is highest in the living crown. At lower heights (up to 12 meters) wood density is also higher just beneath the bark rather than in the pith. The volume shrinkage in aspen wood is largest in the middle of the cross-section pith-surface and smallest close to the pith. Longitudinal shrinkage grew slightly upwards from a height of 3 meters, radial wood shrinkage was the smallest st stump height and at a height of 15 meters and tangential shrinkage was the smallest at a height of 15 meters and it remained quite steady within tree.