Interclonal, Intraclonal, and Within-Tree Variation in Fiber Length of Poplar Hybrid Clones

Variation in fiber length pattern within the stem, within clones, and between clones of the hybrid Populus x euramericana was investigated. Samples were taken from a total of twenty-seven nine-year-old trees representing ten clones from one site in south-central Quebec. Sample disks from each tree were taken from four heights. Each even-numbered ring from the pith was also sampled at each height to determine the radial variation pattern in fiber length. Clones, heights, and the position of annual rings from pith had significant effects on average fiber length. Individual tree broad-sense heritability was 0.41. The main source of variation was the position of annual rings from pith, which-accounted for about 80% of total variance. Fiber length increased from pith to bark for all sampled heights. For a given annual ring, fiber length was low at the bottom of the tree and tended to reach a maximum at mid-height. Weighted average fiber length at breast height was significantly correlated to weighted average fiber length of the merchantable stem. Finally, the correlation between fiber length and growth rate varied over the age of the tree. At early ages, correlation between ring width and fiber length was not significant; at older ages, slight negative but significant correlation was found between these two traits.