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Elevated CO sub(2) affects porewater chemistry in a brackish marsh

As atmospheric CO sub(2) concentrations continue to rise and impact plant communities, concomitant shifts in belowground microbial processes are likely, but poorly understood. We measured monthly porewater concentrations of sulfate, sulfide, methane (CH sub(4)), dissolved inorganic carbon and dissol...

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Bibliographic Details
Published in:Biogeochemistry 2009-12, Vol.96 (1-3), p.101-117
Main Authors: Keller, Jason K, Wolf, Amelia A, Weisenhorn, Pamela B, Drake, Bert G, Megonigal, JPatrick
Format: Article
Language:English
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Summary:As atmospheric CO sub(2) concentrations continue to rise and impact plant communities, concomitant shifts in belowground microbial processes are likely, but poorly understood. We measured monthly porewater concentrations of sulfate, sulfide, methane (CH sub(4)), dissolved inorganic carbon and dissolved organic carbon over a 5-year period in a brackish marsh. Samples were collected using porewater wells (i.e., sippers) in a Schoenoplectus americanus-dominated (C sub(3) sedge) community, a Spartina patens-dominated (C sub(4) grass) community and a mixed (C sub(3) and C sub(4)) community within the marsh. Plant communities were exposed to ambient and elevated (ambient+340ppm) CO sub(2) levels for 15years prior to porewater sampling, and the treatments continued over the course of our sampling. Sulfate reduction was stimulated by elevated CO sub(2) in the C sub(3)-dominated community, but not in the C sub(4)-dominated community. Elevated CO sub(2) also resulted in higher porewater concentrations of CH sub(4) and dissolved organic carbon in the C sub(3)-dominated system, though inhibition of CH sub(4) production by sulfate reduction appears to temper the porewater CH sub(4) response. These patterns mirror the typical divergent responses of C sub(3) and C sub(4) plants to elevated CO sub(2) seen in this ecosystem. Porewater concentrations of nitrogen (as ammonium) and phosphorus did not decrease despite increased plant biomass in the C sub(3)-dominated community, suggesting nutrients do not strongly limit the sustained vegetation response to elevated CO sub(2). Overall, our data demonstrate that elevated CO sub(2) drives changes in porewater chemistry and suggest that increased plant productivity likely stimulates microbial decomposition through increases in dissolved organic carbon availability.
ISSN:0168-2563
1573-515X
DOI:10.1007/s10533-009-9347-3