Authors Name: 
Bridget Murphy
Western University
Earth & Environmental Sciences
Award winner

Future Climate Conditions Alter Leaf Thermotolerance In Canadian Boreal Trees

The Response Of Boreal Tree Species To Projected Increases In Temperature And CO2 Concentration Will Affect The Functioning Of Northern Forests And Could Impact Global Carbon Cycling. As The Climate Warms, Heat Waves Are Expected To Become More Severe And Frequent. Two Common Species In The North American Boreal Forest Are Black Spruce (Picea Mariana [Mill.] BSP) And Tamarack (Larix Laricina [Du Roi] K. Koch). To Determine How Future Climate Conditions Affect Short-Term Heat Tolerance In These Species, I Sampled Seedlings Grown Under Ambient (400 Ppm) Or Elevated (750 Ppm) CO2 Concentrations Combined With Ambient, Ambient +4 C And Ambient +8 C Growth Temperatures And Exposed Needles To Temperatures Between 25 C And 60 C From 3 To 30 Minutes. Electrolyte Leakage From The Needles Was Used As A Proxy For Thermal Damage. To Quantify The Relative Thermotolerance Across Treatments And Species, A Thermotolerance Index Was Created. I Found That Elevated Temperature Increased The Needle Thermotolerance Of Both Black Spruce And Tamarack To Brief, Extreme Heat Exposure. Overall, Elevated CO2 Had Mixed Effects And Only Significantly Increased Thermotolerance In Ambient Temperature Seedlings. Tamarack Did Show Greater Thermotolerance With 10-30% Lower Percent Electrolyte Leakage At All Growth Treatments And Heat Stress Combinations. This Indicates A Potential For Species-Specific Resilience To Predicted Severe Heat Waves. Therefore, Future Climates May Increase Thermotolerance Of Canadian Trees, Reducing Predicted Damage From Climate Change.