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
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  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

  • Adaptive traits
  • Ecological genetics
  • Populus-tremuloides
  • Quantitative genetics

• Graduation date

  Fall 2015

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3PC2TH5P

• 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.