Geochemical control of microbial Fe(III) reduction potential in wetlands: comparison of the rhizosphere to non-rhizosphere soil

dc.contributor.authorWeiss, Johanna V.
dc.contributor.authorEmerson, David
dc.contributor.authorMegonigal, J. Patrick
dc.date.accessioned2007-12-03T16:51:10Z
dc.date.available2007-12-03T16:51:10Z
dc.date.issued2004
dc.description.abstractWe compared the reactivity and microbial reduction potential of Fe(III) minerals in the rhizosphere and non-rhizosphere soil to test the hypothesis that rapid Fe(III) reduction rates in wetland soils are explained by rhizosphere processes. The rhizosphere was defined as the area immediately adjacent to a root encrusted with Fe(III)-oxides or Fe plaque, and non-rhizosphere soil was >0.5 cm from the root surface. The rhizosphere had a significantly higher percentage of poorly crystalline Fe (66±7%) than non-rhizosphere soil (23±7%); conversely, non-rhizosphere soil had a significantly higher proportion of crystalline Fe (50±7%) than the rhizosphere (18±7%, P<0.05 in all cases). The percentage of poorly crystalline Fe(III) was significantly correlated with the percentage of FeRB (r=0.76), reflecting the fact that poorly crystalline Fe(III) minerals are labile with respect to microbial reduction. Abiotic reductive dissolution consumed about 75% of the rhizosphere Fe(III)-oxide pool in 4 h compared to 23% of the soil Fe(III)-oxide pool. Similarly, microbial reduction consumed 75201380% of the rhizosphere pool in 10 days compared to 30201340% of the non-rhizosphere soil pool. Differences between the two pools persisted when samples were amended with an electron-shuttling compound (AQDS), an Fe(III)-reducing bacterium (Geobacter metallireducens), and organic carbon. Thus, Fe(III)-oxide mineralogy contributed strongly to differences in the Fe(III) reduction potential of the two pools. Higher amounts of poorly crystalline Fe(III) and possibly humic substances, and a higher Fe(III) reduction potential in the rhizosphere compared to the non-rhizosphere soil, suggested the rhizosphere is a site of unusually active microbial Fe cycling. The results were consistent with previous speculation that rapid Fe cycling in wetlands is due to the activity of wetland plant roots.
dc.format.extent261662 bytes
dc.format.extent89–100
dc.format.mimetypeapplication/pdf
dc.identifier.citationWeiss, Johanna V., Emerson, David, and Megonigal, J. Patrick. 2004. "<a href="https://repository.si.edu/handle/10088/2994">Geochemical control of microbial Fe(III) reduction potential in wetlands: comparison of the rhizosphere to non-rhizosphere soil</a>." <em>FEMS Microbiology Ecology</em>, 48, (1) 89–100.
dc.identifier.urihttp://hdl.handle.net/10088/2994
dc.language.isoen_US
dc.relation.ispartofFEMS Microbiology Ecology 48 (1)
dc.titleGeochemical control of microbial Fe(III) reduction potential in wetlands: comparison of the rhizosphere to non-rhizosphere soil
dc.typearticle
sro.description.unitserc
sro.identifier.itemID81171
sro.identifier.refworksID96120
sro.identifier.urlhttps://repository.si.edu/handle/10088/2994

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