Ecological and quantitative genetics of Populus tremuloides in western Canada

  • Author / Creator
    Ding, Chen
  • Aspen is a widespread forest tree of high economic and ecological importance in western Canada. The species has also been subject to tree improvement efforts over the past two decades to increase productivity of the forested land base. Successful selection and breeding programs rely on both accurate estimates of the expected genetic gain from selection for commercial traits as well as correlated responses of other traits that may be important for fitness. This thesis investigates geographic patterns of genetic variation observed in a reciprocal transplant experiment with 43 provenances and five sites across western Canada. In a second series of experiments, geographically restricted to Alberta, genetic parameters for growth and adaptive traits are assessed in ten progeny trials containing more than 30,000 trees with known pedigrees. The reciprocal transplant experiment revealed strong patterns of local suboptimality, with increases in productivity as a result of experimental longdistance transfers in northwest direction. For example, provenances moved 1,600 km northwest from Minnesota to central Alberta (a shift of 7° latitude to the north) produced almost twice the biomass of local sources. Increased growth was not associated with lower survival rates. Bud break in provenances transferred northwest generally occurred slightly later than in local sources, suggesting decreased risk of spring frost injury. Leaf abscission was later in provenances transferred in northwest direction, but they appeared to be very frost hardy, well ahead of very rare early fall frost events. A potential explanation for suboptimality is the longevity of aspen clones, where populations could be adapted to climates present during post-glacial recolonization. This hypothesis was explored with habitat reconstructions to the last glacial maximum, which indicated that western Canadian populations likely originated from eastern refugia. We conclude that observed suboptimality likely represents an adaptational lag and benefits in productivity outweigh potential risks iii associated with long-distance northward transfer of aspen planting stock under both current and projected future climate conditions. Progeny trials geographically limited to Alberta seed sources and planting sites revealed high within-population variation in both growth and adaptive traits that was not strongly associated with climatic or geographic variables. Heritabilities for growth and adaptive traits were low to moderate, but progeny trials revealed strong genetic correlations between growth and phenology, with tall trees and high survival being associated with early budbreak and late leaf abscission, which mirrors the results from the provenance trial series across western Canada. While genetic gains in growth traits will be due to expanding the growing season, the increased risk of frost damage in spring and fall does not appear a critical issue, particularly under projected climate warming.

  • Subjects / Keywords
  • Graduation date
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
  • Language
  • Institution
    University of Alberta
  • Degree level
  • Department
    • Department of Renewable Resources
  • Specialization
    • Forest Biology and Management
  • Supervisor / co-supervisor and their department(s)
    • Hamann, Andreas (Renewable Resources)
  • Examining committee members and their departments
    • Hamann, Andreas (Renewable Resources)
    • Brouard, Jean (Isabella Point Forestry Ltd.)
    • Yang, Rong-Cai (Agriculture, Food and Nutritional Science)
    • Hacke, Uwe (Renewable Resources)
    • Landhaeuser, Simon (Renewable Resources)
    • Parker, William (Lakehead University)
    • Macdonald, Ellen (Renewable Resources)