- 199 views
- 262 downloads
Drivers of trembling aspen secondary chemistry and impacts on plant communities in the aspen parkland.
-
- Author / Creator
- Dettlaff, Margarete
-
Plant secondary chemicals are fundamental mechanisms by which plants interact with their environments, including defending against herbivores, attracting pollinators, altering neighbouring plant fitness or facilitating plant-plant communication. Yet our understanding of the extent to which secondary chemicals can impact herbivory has greatly outpaced our understanding of the role of chemistry in impacting other processes. In this thesis, I use trembling aspen (Populus tremuloides Michx.) as a model species to test the hypothesis that variations in the factors that drive plant secondary chemistry may also have the potential to indirectly act as drivers of plant community level processes through the mechanism of plant secondary chemistry. I first asked whether the drivers of aspen chemistry were consistent across the whole plant. I determined that the concentrations of aspen secondary chemicals vary as a function of tissue type, suggesting that drivers of aspen chemistry differ above and belowground. Second, using a regional survey of aspen chemistry, I tested hypotheses about the roles of spatial variation, climate and stand structure as drivers of aspen chemistry. I found that aspen chemistry was more locally variable than would be expected if genetics had the strongest control of chemical concentrations, and that light availability or location within the stand were most associated with changes to aspen chemistry. In my last two chapters, I tested whether these changes to aspen chemistry feedback into, and ultimately impact, understory community assembly and woody encroachment. I found evidence that aspen secondary chemistry might be acting as an ecological filter, as overstory secondary chemical concentrations were associated with changes in understory species richness and evenness. Further, I found evidence that aspen secondary chemistry might facilitate aspen encroachment into invaded habitats, as once a seedling had established, its growth was positively associated with the amount of aspen litter added to a plot. In contrast greater aspen litter inputs were associated with decreased growth in native grasslands.
Combined these findings provide evidence that aspen chemistry is variable, susceptible to changes in the local environment, and that it can directly impact ecological processes. Overall, this suggests that changes in the primary drivers of aspen secondary chemistry could have cascading impacts on an ecological system. Therefore, any changes in the local environment due to climate change or human modifications could have greater impacts on ecosystem processes than expected, as indirect impacts on aspen secondary chemistry are not always accounted for in current ecological models. Broadly, my findings emphasize the importance of including secondary chemical traits and the factors that influence them into trait-based models of community ecology. -
- Graduation date
- Spring 2020
-
- Type of Item
- Thesis
-
- Degree
- Doctor of Philosophy
-
- License
- Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.