Tree population responses to extreme climate events to guide reforestation under climate change

• Author / Creator

  Isaac-Renton, Miriam G

• As climates warm and extreme climatic events occur with more frequency and severity, maintaining forest health and productivity may involve planting seed sources from warmer, drier areas. To guide such reforestation strategies, this work analyzes the risks of both climate change and assisted migration seed transfers using methods from dendrochronology and ecological genetics. Inter-annual growth, drought and frost signatures are studied in tree-ring records from a large provenance trial for lodgepole pine (Pinus contorta Dougl. ex Loud.) in western North America. Results show differences in growth among tree populations to warming, drought and cold under a variety of seed transfer distances. Genotypes from the far south of the range show high drought tolerance, which appears linked to an anisohydric strategy relying on cavitation-resistant xylem. These populations, however, are sensitive to cold and may therefore not be suitable candidates for northward seed transfer under assisted migration. Populations from the central part of the species range are productive, which may be explained by an isohydric strategy related to large xylem conduits. Central populations nevertheless achieve moderate drought tolerance due to lowered inferred stomatal conductance under dry conditions. Central areas may thus not be in immediate need of assisted migration. When grown in southern planting sites, northern genotypes show low drought tolerance as well as susceptibility to spring cold events. Their responses to extreme events indicate that growth benefits from warming may be limited, and that northern boreal forests may be at risk due to increasing climatic variability. Northern areas may therefore benefit from judicious seed transfer from central interior areas. When central interior seed sources are grown in northern environments, they show consistently competitive annual growth relative to local sources, indicating suitability of this possible solution. Generally, however, the intra-specific variation in multiple growth and physiological traits suggest that risks of both climate change and assisted migration vary across species distributions. A cautious and population-oriented approach is recommended for climate-based seed transfer to maintain forest growth and resilience under global change.

• Subjects / Keywords

  • Extreme events
  • Forestry
  • Provenance trials
  • Forest policy
  • Forest maladaptation
  • Climate change
  • Reforestation
  • Water Use Efficiency
  • Weather
  • Drought
  • Dendrochronology
  • Tree rings
  • Wood anatomy
  • Adaptations
  • Frost damage
  • Stable isotope analysis
  • Forest ecology
  • Physiology
  • Assisted migration
  • Cold damage
  • Stable carbon isotope
  • Dendroecology
  • Quantitative forest genetics
  • Ecophysiology
  • Pinus contorta
  • Assisted gene flow
  • Stable oxygen isotope

• Graduation date

  Spring 2018

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3RF5KW74

• 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.