1. to understand growth responses to competition control treatments USING ECOPHYSIOLOGY RESEARCH 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 microclimate Seedling physiology May – October Light (PFD), Ta, RH Soil moisture (SMC), Ts Periodic assessment Net photosynthesis (Pn), etc. Relative growth rates

4. White pine restoration and shelterwood sites (ON) 1.Treatments: none (C), herbaceous only (H), woody only (W), and both (B) 2.Microclimate – growing seasons 1- 4 3.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) 1.Treatments: none (C), herbaceous only (H), woody and herbaceous (B), radial woody only (RW), radial both (RB) 2. Microclimate – growing seasons 1- 4 3. 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: 1.Minimum air temperature 2.Light levels after frost event

21. Lower temperature and higher light increase frost damage

22. White pine in clearcuts: Competition for light and H 2 O 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!! Conclusions