Kathryn Schoenecker's Ph.D. defense
Friday, September 7, 2012, 01:30 PM
Natural and Environmental Sciences Building (NESB), B215

GDPE student Kathryn Schoenecker's Ph.D. defense

Plant response to herbivory is plastic and varies depending on multiple environmental conditions. The idea that grazing may benefit vegetation in some way was first proposed in 1960 in a botanical review of grazing on rangelands. This potential benefit was later described by the herbivore optimization hypothesis, which predicts an increase in aboveground net primary productivity (ANPP) at moderate grazing intensities up to some optimum, and a decrease with continued grazing. The increase in performance has also been defined as plant “tolerance” or “compensation.” I conducted research to understand the response of plants to herbivory and identify potential constraints on plant compensation in an arid ecosystem. I used a replicated herbivore exclusion experiment to evaluate herbaceous plant and woody species response to grazing by large ungulates. I measured utilization, N-yield, and herbaceous and woody species production in different vegetation communities of the San Luis Valley, Colorado. I stratified by predominant ungulate species to evaluate differences in vegetation response in areas with elk plus bison herbivory and areas with just elk herbivory, and used fenced exclosures to conduct ungrazed treatments from 2005 to 2009. Results from my research show that there were few differences in herbaceous offtake or production between ungulate strata. I found that herbaceous vegetation overcompensated for tissue loss from herbivores, and woody plants mostly undercompensated. However, in some areas woody plants did not respond to removal of browsing even after 5 years of exclosure, suggesting water and climate drivers influence these woody plants more strongly than herbivory.

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Event Contact: Jeri Morgan can be reached at (970) 491-4373

Sponsored by the Graduate Degree Program in Ecology.