HR: 11:00h
AN: B42A-03    [Abstracts]
TI: Carbon Cycling in Soils of the McMurdo Dry Valleys, Antarctica
AU: * Barrett, J E
EM: jebarre@vt.edu
AF: Department of Biological Sciences, Virginia Tech, 1010 Derring Hall, Blacksburg, VA 24061, United States
AB: The Antarctic Dry Valleys are among the most extreme soil environments on earth. In 1903 R.F. Scott wrote of an apparent lack of life in the dry valleys, yet recent evidence reveals microbial and invertebrate abundances comparable to hot deserts. While Scott's impression has persisted far into modern times, an emerging view of dry valley biogeochemistry suggests a greater potential for biological activity and influence over element cycling than recognized in the early years of Antarctic exploration and research. For example, due to the lack of vascular plants in the dry valleys, soil organic matter was historically thought to be derived from allochthonous inputs of carbon, but recent evidence shows that soil organic carbon and nitrogen pools have multiple origins, including lacustrine, marine, endolithic and in situ sources derived from both ancient and contemporary processes. Here I present a synthesis of data describing dry valley soil organic matter pools and processes; including a model for soil carbon turnover based upon in situ mineralization rates and kinetic fractionation techniques. Rates of in situ carbon mineralization are among the lowest reported for terrestrial ecosystems, yet estimates of residence times for carbon are shorter than might be expected in an ecosystem so strongly influenced by landscape legacies carried over from the Last Glacial Maximum. Rate kinetics for carbon mineralization indicate that organic matter may cycle over multiple time scales consistent with both ancient and contemporary sources. This model suggests that a slow turnover pool of soil carbon is stable over century to millennial time scales, while a smaller carbon pool cycles more rapidly and responds to seasonal and inter- annual climate variability. This model demonstrates how multiple pool models of soil carbon can account for the apparent paradox of rapid carbon turnover in an ecosystem influenced by biogeochemical legacies.
DE: 0400 BIOGEOSCIENCES
DE: 0438 Diel, seasonal, and annual cycles (4227)
DE: 0456 Life in extreme environments
DE: 0470 Nutrients and nutrient cycling (4845, 4850)
DE: 0475 Permafrost, cryosphere, and high-latitude processes (0702, 0716)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting