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Comparison of defense-associated secondary metabolites across varying level of deer herbivory

Project Abstract: 
Following up on findings of a 2017 research project conducted by EEB 348 Forest Ecosystem students (Agee et al. 2017), we propose to quantify sapling chemical defense as a response to deer herbivory. Plants that evolve with mammalian herbivores develop physical mechanisms to deter mammalian browsing, e.g., spines and thorns. However, northern hardwood forest tree species likely did not evolve with the high deer densities found today in Northern Michigan and therefore lack these physical defenses. Chemically, plants can synthesize defense-associated secondary metabolites in response to insect herbivory, but more research is needed to better understand metabolites associated with mammalian browsing, specifically by white-tailed deer. Data from Agee et al. (2017) yielded a positive correlation between phenolic compounds and time since the sapling was browsed (a measure of browsing intensity). In order to better understand these findings, we propose to quantify defense-associated compounds in commonly browsed sapling species and compare types and concentrations of compounds, 1) in mammalian-browse vs. unbrowsed saplings, and 2) across varying levels of browse intensity.
Investigator(s): 
Years Active: 
2018
Methods: 
We will collect bud and leaf samples of Acer rubrum, Fagus grandifolia, and Quercus rubra both inside and outside of UMBS deer exclosures. No more than five samples of each species will be collected from within the exclosures. Ten samples from each species will be collected outside of exclosures and within 100 m of exclosure. For samples collected within the exclosure, all saplings will be tagged at base of sapling with metal tag on a loosely fit zip tie, and the branch where sample was taken will be marked with pink flagging. Saplings outside of exclosures will be marked with temporary flagging. Time since last browsing event will be estimated for each sapling using the Twig-age method (Waller et al. 2017). Bud and leaf samples will be analyzed for defense-associated compounds in the UMBS Analytical Services Lab. Samples will be collected during Spring/Summer 2018. Laboratory and data analyses will take place during Summer 2018.
Funding agency: 
UM Flint grant (Mott Foundation) to fund summer student research (stipend only)