Oral Session # 35: Biogeochemistry III: Arctic, Alpine, and Tundra Systems.
Presiding: A Hartley
Tuesday, August 5. 1:30 PM to 5:00 PM, SITCC Meeting Room 203.

Stoichiometric evolution of Antarctic Dry Valley landscapes.

Barrett, J*,1, Virginia, Ross1, Wall, Diana2, Lyons, William3, 1 Dartmouth College, Hanover, NH, USA2 Natural Resource Ecology Laboratory, Fort Collins, CO, USA3 The Ohio State University, Columbus, OH, USA

ABSTRACT- Alfred Redfield′s concept of elemental stoichiometry describes how organisms influence, and are influenced by the chemical composition of their environment. This general approach has provided a useful framework for understanding nutrient dynamics across the Earth′s major biomes. In the polar desert of the McMurdo Dry Valleys, Antarctica, physical processes are the dominant control over ecosystem development and the affect of biology on the chemical environment is relatively inconspicuous. The dry valleys hence provide a unique opportunity to evaluate the stoichiometric approach and the relative influences of biotic vs. abiotic controls over ecosystem development across landscape units comprising a gradient of biological activity and production, i.e. soils, streams and lakes. We report that biotic control over C:N:P is poorly expressed in soils of the dry valleys, while wider C:N and C:P ratios in the aquatic ecosystems reflect important biological influences over ecosystem stoichiometry. C:N:P ratios widen across landscape units from soils, to streams to lakes. In the oldest and most extreme soil environments, C:N:P ratios are not different from the parent material, while the wide C:P ratios of stream water and some lakes indicate severe P deficiency and significant biotic control over the availability of nutrient elements. Based upon these data we conclude that the elemental stoichiometry of dry valley ecosystems is ultimately regulated by geomorphic processes operating over long time scales, while biotic communities may affect local C and N availability in productive ecosystems over seasonal to annual cycles. The exchanges of C, N and P across these ecosystems, facilitated by hydrology and glaciation, link the landscape units of the dry valleys.

Key words: McMurdo Dry Valleys, biogeochemistry, Redfield ratios, stoichiometry