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 re presenting ten clones from one site in south-central Quebec. Sample di sks from each tree were taken from four heights. Each even-numbered ri ng from the pith was also sampled at each height to determine the radi al variation pattern in fiber length. Clones, heights, and the positio n of annual rings from pith had significant effects on average fiber l ength. Individual tree broad-sense heritability was 0.41. The main sou rce of variation was the position of annual rings from pith, which acc ounted for about 80% of total variance. Fiber length increased from pi th to bark for all sampled heights. For a given annual ring, fiber len gth 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 signif icantly correlated to weighted average fiber length of the merchantabl e stem. Finally, the correlation between fiber length and growth rate varied over the age of the tree. At early ages, correlation between ri ng width and fiber length was not significant; at older ages, slight n egative but significant correlation was found between these two traits .