• Yanchuck, A. D.
  University of Alberta
  
• Dancik, B.P.
  University of Alberta
  
• Micko, M.M.
  

Fifteen putative trembling aspen (Populus tremuloides Michx.) clones in north-central Alberta were sampled to examine patters of variation and determine the heritability of wood density and fibre length among clones. Large increment cores from the southern radius at breast height of each of five to nine trees in each clone were divided into four-year sections from the pith outward. All trees sampled were at least 36 years of age. Wood density measurements were made on each four-year section, and fibre lengths were measured on every second four-year increment period.

There were significant clonal differences for both wood density and fibre length. Broad-sense heritabilities for wood density and fibre length were 0.35 and 0.43 respectively. Wood density is generally high near the pith, decreases substantially a short distance from the pith, then increases in the mature wood zone. Fibre length is short near the pith and increases markedly across the radius. There was a slight negative phenotypic correlation between wood density and growth rate and a slight positive phenotypic correlation between fibre length and growth rate. Genetic correlations indicated there relationships are under moderate genetic control.