Date of Award:
Master of Science (MS)
Dale L. Bartos
Quaking aspen (Populus tremuloides) clones within close proximity to one another can exhibit drastically different levels of browsing by ungulates. The objectives of this study were to (1) determine interclonal differences in plant chemistry between adjacent clones exhibiting different degrees of herbivory which may influence the browsing behavior and patterns of ungulates, and (2) determine if correlation exists in the levels of salicortin and tremulacin between current year's suckers and current year's growth on older trees. This second objective was meant to indicate a protocol for land managers for identifying clones meriting increased protection from herbivory after treatment and wildfire.
In July of 2005, 6 pairs of clones were identified on the Dixie National Forest, Utah, and on Cedar Mountain, east of Cedar City, Utah. Pairs consisted of 2 clones within the same pasture and/or grazing allotment and within a minimal distance from one another; one clone displaying moderate to high levels of ungulate utilization of aspen suckers, and one exhibiting minimal to no ungulate utilization of aspen suckers. Soil samples were taken at each clone and leaf tissues were sampled to determine genet. Aspen suckers were sampled for nutrient content, combined phenolic glycoside concentration (salicortin and tremulacin), condensed tannins, and the presence of extra floral nectaries (EFNs), at intervals throughout the growing season (August 3-6, August 31-September 2, and October 12-14). Current year's growth from representative mature trees was sampled for phenolic glycoside concentration at these times as well.
All tests demonstrated high levels of insignificance for both leaves and stems.Sucker nitrogen values may have been elevated during portions of the sampling year in clones displaying moderate to high levels of ungulate utilization, possibility indicating an ungulate preference for nitrogen, but due to missing values, this is far from conclusive.
P-values for forest floor factors were also highly non-significant with the exception of forest floor C (0.04) in the regenerating clones. Two post-project hypotheses are postulated in an attempt to explain the differences of forest floor carbon in terms of factors that may be influencing ungulate herbivory.
Winter, Damon A., "Interclonal Variation of Primary and Secondary Chemistry in Western Quaking Aspen and its Influence on Ungulate Selection" (2010). All Graduate Theses and Dissertations. 856.
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