Five Points Small Mammal Blood Plasma Isotopic Values for Carbon, Nitrogen and Hydrogen


There has been little comprehensive research undertaken to quantify resource use by small mammal communities in a nutrient limited, highly stochastic ecosystem. The most abundant small mammals in this ecosystem are Heteromyids, food-caching granivores, and Cricetids, omnivores that must utilize on board fat stores as energy reserves. Heteromyid populations co-vary with primary production whereas the cricetids can forage at multiple trophic levels reducing their dependence on primary productivity. Using isotopic values for Carbon, 13C (a ratio of 13C to 12C), of primary producers consistent within a photosynthetic pathway, C3 = -26.6 +/- 1.8‰ and C4, = -14.4 +/- 0.8‰ we can track mouse dietary assimilation of forage by plant functional type (Craig et al. 1953, Farquhar 1989). Nitrogen isotopic values 15N (a ratio of 15N to 14N) fluctuate constantly, reflecting the landscape of primary production. Therefore, tracking nitrogen values in small mammal plasma provides a landscape level tool for studying diet by trophic level and nutritional value.

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