Adaptation of white spruce to climatic risk environments in spring: implications for management under climate change

  • Author / Creator
    Casmey, Mariah
  • The timing of spring dormancy release and bud break in trees is an adaptive trait with potentially important management implications. Depending on how spring phenology is controlled, climate warming may disrupt the synchronization of bud break with the available growing season. Further, addressing climate change through human assisted migration in reforestation programs could cause additional problems if phenology triggers of source and target locations differ. Here, we assess how phenology is controlled by heat sum and chilling requirements for a widespread and commercially important boreal tree species, white spruce (Picea glauca) in a range-wide common garden experiment. We find significant genetic population differentiation in heat sum requirements ranging from 390 to 450 degree days among regions (±12 average SE), and from 375 to 500 (±16) degree days among populations within regions. The lowest heat sum requirements are present in populations originating from climate environments with short growing seasons and high rates of spring warming. Chilling requirements in white spruce were also found (approx. 15 degree days), but they showed no genetic population differentiation. The results imply an evolutionary strategy of white spruce to take full advantage of a restricted northern boreal growing season. We can also infer that assisted migration of southern sources poleward is safe, but may entail a competitive disadvantage due to late bud break relative to local populations. Due to generally low chilling requirements, we do not anticipate de-synchronization of spring phenology with the growing season under climate warming in spruce, which could occur if high chilling requirements are not met.

  • Subjects / Keywords
  • Graduation date
    Fall 2022
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Library 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.