Meeting Abstract
55.5 Saturday, Jan. 5 Small Mammal Utilization of Pulsed Resources Quantified through Stable Isotope Analysis PERSHALL, A.D.*; WARNE, R.; WOLF, B.O.; University of New Mexico; University of New Mexico; University of New Mexico alaina@unm.edu
In this study we examine rain-driven pulses of production in C3 and C4 plant functional groups and use stable isotope analysis to quantify how these pulses influence nutrient flux from plants to rodents and rodent population dynamics. Our research site, which is located at the Sevilleta NWR/LTER in the Chihuahuan Desert of New Mexico, is characterized by a bimodal rainfall pattern where C3 plants increase production in response to winter rains and C4 plants respond to summer monsoons. From 2005 to 2006, New Mexico experienced a shift from high winter and low summer precipitation to low winter and high summer precipitation, changing the seasonal plant composition. C3 and C4 plants differ in δ13C isotopic composition because of different photosynthetic pathways and δ15N increases 3.3� per trophic level. We collected blood plasma monthly, which indicates an animal�s diet during the previous 5-7 days, and analyzed the plasma for δ13 C and δ15N. Plasma δ13 C and δ15N values were compared to the δ 13C and δ15N of vegetation and arthropods to quantify rodent diet composition. From April to November 2005, plasma δ13C enriched for some rodents indicating a shift from C3 to C4 plant utilization. In 2006, when C3 plant production decreased, all species increased diet variablility and reliance on C4 plants. δ13C enrichment patterns reflected diet and habitat specialization and δ15N values further revealed resource driven trophic dynamics within this food web. Further results may show how changes in abundance and availability of plant functional groups, that occur with climate change, not only affect rodent diets but possibly survival, population size and species diversity.
