Investigating trade-offs using ecological stoichiometry in the boreal forest

Richmond, Isabella Croft (2020) Investigating trade-offs using ecological stoichiometry in the boreal forest. Masters thesis, Memorial University of Newfoundland.

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Abstract

Studying trade-offs allows for the investigation of complex ecosystem interactions and processes. Ecological stoichiometry measures the elemental ratios and the balance of ratios in organisms and allows for comparisons across species, populations, and ecosystems. I tested two questions regarding ecological trade-offs. First, I tested whether there is interannual variation in the stoichiometric traits of boreal plant species and, if so, what is driving the variation. Second, I tested how herbivore space use is influenced by perceived predation risk and food quality. I found that interannual variation occurs in percent carbon for all species and that the evergreen conifer was the only species that experienced interannual variation in other elements. I found temperature, moisture, and productivity to be drivers of interannual variation. For the second question, I found that snowshoe hare space use is influenced by perceived predation risk and food quality. These factors interact and produce an effect at the individual level, where hares increase space use in high risk areas if there is high-quality food and vice versa. Predation risk and plant stoichiometry are connected through their shared impact on foraging behaviour, which influences herbivore life cycles. This work establishes ecological stoichiometry as an exciting framework to investigate biological trade-offs and contributes to our understanding of the temporal variation of resources and herbivore space use.

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