SHRINKAGE OF FAST-GROWING HYBRID POPLAR CLONES

Twenty-eight 9-year-old trees from 10 clones of the hybrid Populus x e uramericana at one site in south central Quebec were sampled to study the pattern of wood shrinkage variability within trees, within clones, and between clones. Four small standard specimens and a 10-mm-diamete r increment core were taken from each tree at breast height. Partial a nd total radial, tangential, and volumetric shrinkages were evaluated from both types of specimens. Results indicated that clones show highl y significant differences in shrinkage behavior. The effect among tree s within the same clone was significant but accounted for less than 5 percent of the total variation. The tangential and volumetric shrinkag es increased from pith to bark and tended to level off near the bark. Shrinkage values of clearwood and 10-mm increment cores were significa ntly correlated. However, shrinkage was only moderately correlated to wood density. Finally, no significant relationship was found between g rowth rate and shrinkage values.