Date of Award
H. Thomas Goodwin
A previous Honors study analyzed diet of thirteen-lined ground squirrels at the Andrews University Airpark by studying δ13C and δ15N isotope values of their fecal pellets (Chacko, 2013). Fecal samples collected within 25m of a cornfield had elevated isotope values.
High δ13C values indicate greater consumption of C4 plants, such as corn (Ehleringer et al., 1986); high δ15N values indicate increased consumption of animal matter (DeNiro and Epstein, 1981 ). However, the spatial pattern may be due to variation in the soil, reflecting long-term patterns in the vegetation.
Soil samples were taken throughout the airpark and analyzed for δ13C and δ15N. These baseline values were removed from fecal values, but the patterns of the fecal samples still held.
Application of fertilizer to vegetation resulted in a significant increase in δ15N. Thus, the δ15N pattern observed in the fecal samples appears to be due to enrichment in corn.
Kim, Jamie and Goodwin, H. Thomas Ph.D., "Investigation of Spatial Isotope Ratios in Soil and the Effects of Fertilizer on Plant Isotope Ratios" (2014). Posters, Presentations, and Papers. 2.
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