The Influence of Aspen Chemistry and the Nutritional Context on Aspen Herbivory

Author

Kristen Y. Heroy, Utah State UniversityFollow

Date of Award:

5-2017

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Wildland Resources

Committee Chair(s)

Juan J. Villalba

Committee

Juan J. Villalba

Committee

Samuel B. St. Clair

Committee

Paul C. Rogers

Committee

Johan du Toit

Committee

Eric Thacker

Committee

Jeffery O. Hall

Abstract

Consumption of aspen by herbivores is one major force causing aspen decline in North America. In this Dissertation, I aimed to determine why herbivores prefer browsing on certain aspen stands over others, and why they prefer consuming aspen that contains chemical defenses over understory forages like grasses, forbs, and shrubs. I explored the influence of nutrients and chemical defenses within aspen on aspen intake and preference by lambs in pen experiments. I also explored drivers of aspen preference on the landscape by looking at relationships between aspen herbivory, indicators of aspen health, amount of nutrients available in the understory, and chemical defenses in aspen leaves.

I found that as dietary protein and energy increased or decreased, respectively, lambs increased the amount of aspen consumed, and these effects were greater when chemical defenses in aspen leaves occurred at low concentrations. In addition, when lambs were presented with a choice between aspen stands of contrasting concentrations of chemical defenses (high vs. low), other nutrients in aspen leaves (e.g., minerals, protein), or prior experience that lambs had with high-protein rations were more important at driving aspen preference than chemical defense content. On the landscape, aspen health was better at high elevations where amounts of crude protein and grasses were greater than at lower elevations. A negative association was found between aspen herbivory and concentration of chemical defenses, and between elk presence (measured by fecal pellets) and the amount of protein in the understory.

Checksum

a7ef6fc1b73a2a1f1aa29d6183aa86b3

Recommended Citation

Heroy, Kristen Y., "The Influence of Aspen Chemistry and the Nutritional Context on Aspen Herbivory" (2017). All Graduate Theses and Dissertations, Spring 1920 to Summer 2023. 6479.
https://digitalcommons.usu.edu/etd/6479