P-17 Investigation of spatial isotope ratios in soil and the effects of fertilizer on plant isotope ratios
Abstract
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. Fecal samples collected within 25 m of a cornfield had higher mean values of δ13C and δ15N than those outside that range. High δ13C values indicate greater consumption of C4 plants, such as corn, while high δ15N values may indicate increased consumption of insects. However, the spatial pattern might simply reflect spatial variation in the isotope values of the soil itself, reflecting long-term pattern isotope values in vegetation. In this experiment, soil samples were taken throughout the airpark and analyzed for δ13C and δ15N; these baseline values were removed from fecal isotope values. The spatial isotope patterns of fecal pellets still held after baseline removal. Therefore, it appears that the spatial pattern of δ13C seen in the fecal samples of the thirteen-lined ground squirrels is indeed due to greater consumption of corn. The pattern of δ15N could either be due to increased consumption of insects or enrichment of corn in δ15N due to fertilizer application. Further study is in progress to see the effects of fertilizer application on plant δ13C and δ15N.
Location
Buller Hallway
Start Date
3-7-2014 2:30 PM
End Date
3-7-2014 4:00 PM
P-17 Investigation of spatial isotope ratios in soil and the effects of fertilizer on plant isotope ratios
Buller Hallway
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. Fecal samples collected within 25 m of a cornfield had higher mean values of δ13C and δ15N than those outside that range. High δ13C values indicate greater consumption of C4 plants, such as corn, while high δ15N values may indicate increased consumption of insects. However, the spatial pattern might simply reflect spatial variation in the isotope values of the soil itself, reflecting long-term pattern isotope values in vegetation. In this experiment, soil samples were taken throughout the airpark and analyzed for δ13C and δ15N; these baseline values were removed from fecal isotope values. The spatial isotope patterns of fecal pellets still held after baseline removal. Therefore, it appears that the spatial pattern of δ13C seen in the fecal samples of the thirteen-lined ground squirrels is indeed due to greater consumption of corn. The pattern of δ15N could either be due to increased consumption of insects or enrichment of corn in δ15N due to fertilizer application. Further study is in progress to see the effects of fertilizer application on plant δ13C and δ15N.
Acknowledgments
J.N. Andrews Honors Scholar and Undergraduate Research Scholarr
Advisor: H. Thomas Goodwin, Biology