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Effects of intercropping switchgrass with Loblolly pine on the diet and trophic position of Peromyscus leucopus

UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
Kim M. Briones (Creator)
Institution
The University of North Carolina at Greensboro (UNCG )
Web Site: http://library.uncg.edu/
Advisor
Matina Kalcounis-Rueppell

Abstract: Managed pine plantations have been recognized as potentially suitable land for producing biofuel feedstocks. Intercropping biofuel feedstocks, particularly switchgrass ((Panicum virgatum L., a native C4 grass), in existing loblolly pine (Pinus taeda) plantations is a potentially sustainable alternative to land conversion for feedstock production. However, little is known about how biofuel feedstock intercropping could affect biodiversity and ecosystem functioning in a managed forest system. I conducted a study of a common native omnivore, the white-footed mouse (Peromyscus leucopus), to examine if they would use planted switchgrass as a food source, or if they would use existing food resources associated with pine. This study was one of the first to examine ecological effects of forest management of biofuel feedstocks on a key forest consumer. Rodents were live trapped in four replicates of three different treatments planted with: (1) pine only, (2) pine intercropped with switchgrass and (3) switchgrass-only. I assessed the diet sources and trophic position of mice using stable isotopes of carbon (δ13C) and nitrogen (δ15N), respectively, in tissue samples collected in 2009 and 2010. I tested the hypothesis that switchgrass in intercropped landscapes would affect the dietary preference and trophic position of (P. leucopus. In terms of intercropping, my main prediction was that diet and trophic position of mice in intercropped treatments would reflect a C3/C4 signal and trophic position would be lower than treatments with pine only, indicating a change in functional role. In 2009 there was no effect of treatment, but there was an effect of season on diet and trophic position of (P. leucopus. Across both seasons, mice consumed a combined C3/C4-based diet. However, in the summer, diet in all treatments was slightly more C4-influenced, whereas in the fall diet was slightly more C3-influenced. However, the influence was not dramatic in either season. Additionally, trophic position was higher in the fall and lower in the summer. In 2010, mouse diets in all treatments reflected a combined C3/C4-based diet. There was no effect of treatment or season on diet, but δ13C of mouse tissue in switchgrass only treatments was pulled slightly toward a C4 signal. In terms of trophic position, d15N values indicated that mice remained functionally omnivorous. While these findings did not suggest an influence of switchgrass on diet or trophic position of (P. leucopus, results are based on only the first two years of the intercropping study. As treatments become more established, further study should be conducted to ensure that ecological roles of consumers remain intact.

Additional Information

Publication
Thesis
Language: English
Date: 2011
Keywords
Switchgrass, Loblolly Pine, Peromyscus leucopus, Panicum virgatum,
Subjects
Peromyscus leucopus $x Effect of forest management on $z North Carolina
Peromyscus leucopus $x Habitat $z North Carolina
Loblolly pine $x Research $z North Carolina
Switchgrass $x Research $z North Carolina
Forest management $x Research $z North Carolina