The potential of aspen clones and hybrids for enhanced forest management in Alberta

This thesis presents results from an industrial aspen tree improvement program for Alberta, evaluating a series of provenance, clonal and hybrid field trials. The goals were to (1) investigate geographic patterns of genetic variation in order to delineate breeding regions, (2) to assess the potential of clonal forestry systems to enhance forest productivity, and (3) to evaluate the potential of hybridization to enhance growth through hybrid vigor. Partitioning of genetic variance with geographic predictor variables suggests two breeding regions for Alberta should be appropriate: a Sub-Boreal Rocky Mountain Foothill region between 52°30’N and 56°N latitude, and a Boreal Mixedwood region between 56°N and 59°N latitude. Broad-sense heritabilities for height and diameter ranged from 0.36 to 0.64 on selected sites, allowing 5-15% genetic gains in height and 9-34% in diameter based on selections from current trials. The best genotypes within hybrid families could have some additional potential in improving yields.