to understand growth responses to competition control treatments USING ECOPHYSIOLOGY RESEARCH Bill Parker – Ontario Forest Research Institute and Doug Pitt – Canadian Forest Service
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
Seedling microclimate Seedling physiology May – October Light (PFD), Ta, RH Soil moisture (SMC), Ts Periodic assessment Net photosynthesis (Pn), etc. Relative growth rates
White pine restoration and shelterwood sites (ON) 1.Treatments: none (C), herbaceous only (H), woody only (W), and both (B) 2.Microclimate – growing seasons Seedling physiology – growing seasons 2- 4
Soil moisture availability differs with treatment over time
Light availability differs with treatment over time
Treatments affect photosynthesis through light and SMC
Growth driven by treatment effects on light and soil warming
In shelterwoods, less treatment influence on soil moisture…
…and light due to the dominant effect of overstory on microclimate / resources
Treatments affect photosynthesis through light and SMC
Growth driven by treatment effects on light
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 Seedling physiology – growing seasons 3 - 4
Treatments have little effect on soil moisture availability
Radial and broadcast woody control increase light levels
Treatments have little effect on photosynthesis
Light and humidity interact to regulate photosynthesis
Leaf gas exchange of white spruce is sensitive to humidity
This response improves WUE in open environments
Do competition control treatments influence spring frost damage? Damage is dependent on: 1.Minimum air temperature 2.Light levels after frost event
Lower temperature and higher light increase frost damage
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