The within-tree variation in wood density and shrinkage, and their relationship in Populus euramericana

The patterns of wood density and shrinkage in different directions in 22-year-old Populus euramericana trees from one clone were studied in an experimental plantation in Iran. Sample disks were taken from each tree to examine wood density and shrinkage variation from pith to bark at 5%, 25%, 50%, and 75% of total tree height. The results indicate that radial position and height significantly affected all wood physical properties. Within-tree wood density and shrinkage varied at each height level, decreasing along the stem from the base upwards. Moreover, within the samples, at the same height level wood density and shrinkage in the radial direction increased from the pith outwards. Regression analysis showed that longitudinal, radial, tangential, and volumetric shrinkage each had a significantly positive correlation with wood density.