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Growth Responses to Competition Control Treatments in White Pine and White Spruce Regeneration

Using ecophysiology research to understand the effects of different treatments on growth responses of white pine and white spruce, including factors like light availability, soil moisture, and susceptibility to damage.

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Growth Responses to Competition Control Treatments in White Pine and White Spruce Regeneration

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  1. USING ECOPHYSIOLOGY RESEARCH to understand growth responses to competition control treatments Bill Parker – Ontario Forest Research Institute and Doug Pitt – Canadian Forest Service

  2. Key ecological features of white pine and white spruce regeneration • Intermediate in shade tolerance, slow initial growth • Favoured by sheltered, moderate microenvironment • Maximum height growth at 50% sunlight • Maximum diameter and volume at 100% sunlight • Weevil and blister rust damage to open grown white • pine seedlings • Susceptibility of white spruce to spring frost damage

  3. Seedling physiology Seedling microclimate • Periodic assessment • Net photosynthesis (Pn), etc. • Relative growth rates • May – October • Light (PFD), Ta, RH • Soil moisture (SMC), Ts

  4. White pine restoration and shelterwood sites (ON) • Treatments: none (C), herbaceous only (H), woody only (W), and both (B) • Microclimate – growing seasons 1- 4 • Seedling physiology – growing seasons 2- 4

  5. Soil moisture availability differs with treatment over time

  6. Light availability differs with treatment over time

  7. Treatments affect photosynthesis through light and SMC

  8. Growth driven by treatment effects on light and soil warming

  9. In shelterwoods, less treatment influence on soil moisture…

  10. …and light due to the dominant effect of overstory on microclimate / resources

  11. Treatments affect photosynthesis through light and SMC

  12. Growth driven by treatment effects on light

  13. Boreal mixedwood site (ON) • Treatments: none (C), herbaceous only (H), woody and herbaceous (B), radial woody only (RW), radial both (RB) • Microclimate – growing seasons 1- 4 • Seedling physiology – growing seasons 3 - 4

  14. Treatments have little effect on soil moisture availability

  15. Radial and broadcast woody control increase light levels

  16. Treatments have little effect on photosynthesis

  17. Light and humidity interact to regulate photosynthesis

  18. Leaf gas exchange of white spruce is sensitive to humidity

  19. This response improves WUE in open environments

  20. Do competition control treatments influence spring frost damage? • Damage is dependent on: • Minimum air temperature • Light levels after frost event

  21. Lower temperature and higher light increase frost damage

  22. Conclusions • White pine in clearcuts: • Competition for light and H2O • with herbaceous and woody • vegetation • White pine in shelterwoods: • Competition for light is most • important • Boreal mixedwood: • Sheltered environment assists • white spruce regeneration • Thanks to all for their support!!

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