HR: 16:45h
AN: B24A-04 INVITED    [Abstracts]
TI: Microbial and Nutrient Responses to Enhanced Availability of Nitrogen, Phosphorus, and Carbon Dioxide in a California Grassland
AU: * Gurwick, N P
EM: ngurwick@globalecology.stanford.edu
AF: Carnegie Institution, Department of Global Ecology 260 Panama Street, Stanford, CA 94305, United States
AU: Gessner, M
EM: Mark.Gessner@eawag.ch
AF: Eawag, Überlandstrasse 133 P.O. Box 611, Dübendorf, 8600, Switzerland
AU: LE ROUX, X
EM: leroux@biomserv.univ-lyon1.fr
AF: CNRS Université Lyon, Microbial Ecology Centre UMR 5557 USC 1193 INRA Bat G. Mendel 43 bd du 11 novembre 1918, Villeurbanne, 69622, France
AU: Poly, F
EM: poly@biomserv.univ-lyon1.fr
AF: CNRS Université Lyon, Microbial Ecology Centre UMR 5557 USC 1193 INRA Bat G. Mendel 43 bd du 11 novembre 1918, Villeurbanne, 69622, France
AU: Chiariello, N
EM: nonajrbp@stanford.edu
AF: Stanford University, Herrin Labs Stanford University, Stanford, CA 94305,
AU: Field, C B
EM: cfield@globalecology.stanford.edu
AF: Carnegie Institution, Department of Global Ecology 260 Panama Street, Stanford, CA 94305, United States
AU: Vitousek, P M
EM: vitousek@stanford.edu
AF: CNRS Université Lyon, Microbial Ecology Centre UMR 5557 USC 1193 INRA Bat G. Mendel 43 bd du 11 novembre 1918, Villeurbanne, 69622, France
AU: Vitousek, P M
EM: vitousek@stanford.edu
AF: Stanford University, Herrin Labs Stanford University, Stanford, CA 94305,
AB: We here report results from a full factorial manipulation of CO2, N, and P availability, using mesocosms planted with six species common to California grasslands. The experiment was conducted in the field as a companion study to the Jasper Ridge Global Change Experiment and was designed to evaluate the role of P limitation as a constraint on ecosystem responses to rising CO2 concentrations and N deposition. This presentation will focus on belowground responses, although the larger study included many aboveground components. Response variables considered here include nutrient fluxes through soil (measured using resin strips), bacterial production and potential nitrification. Preliminary analyses revealed that enhanced N deposition led to increased soil N trapped on resin strips, but only under ambient CO2 and P. Bacterial production and potential activity of nitrite oxidizers both increased in response to P additions, and bacterial production responded positively to N but only under ambient P. These data suggest an increase in belowground allocation by plants in response to enhanced CO2. Increased C availability belowground would be expected to increase production of heterotrophic but not autotrophic microbes (i.e., nitrifiers). Increased nutrient demand under elevated CO2 suggested by resin strip data could result either from direct plant uptake or from enhanced microbial activity. The positive response of both heterotrophic and autotrophic bacteria to P additions suggests that microbial immobilization, in addition to plant uptake, explains the decline in resin N in response to P enrichment.
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 0469 Nitrogen cycling
DE: 0470 Nutrients and nutrient cycling (4845, 4850)
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting