Meeting Abstract
P1.17 Jan. 4 Small mammal utilization of pulsed resources quantified through stable isotope analysis PERSHALL, A.D.*; WARNE, R.W.; WOLF, B.O.; 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 resource pulses influence nutrient flux from plants to rodents and rodent population dynamics. Our site at the Sevilleta NWR/LTER, in the Chihuahuan Desert of New Mexico, is composed of a mixture of C3 and C4 plants. The Spring C3 plants increase production in response to winter rains and summer dominant C4 plants respond to the 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 samples monthly, which indicates an animals diet during the previous 5-7 days, and analyzed these for δ13C and δ15N. These values were compared to the δ13C and δ15N of vegetation and arthropods to quantify their relative proportions in the diet of rodents through time. Plasma δ13C from April to November 2005 showed an enrichment for some rodents, indicating increased utilization of C4 plants as those plants increased production. These enrichment patterns were species specific reflecting diet and habitat specialization. Analysis of δ15N further revealed resource driven trophic dynamics within this rodent food web. While the amount and timing of rainfall is important to C3 and C4 plant production further results may show how changes in abundance and availability of different plant functional groups not only affect rodent diets, but possibly survival, population size and species diversity.
