56-5 Rhizogenic Fe Redox Cycling: A Biogeochemical Process Linking Uplands and Wetlands

See more from this Division: Joint Sessions
See more from this Session: Soils through Time: Critical Zone Studies of Processes and Their Effects

Monday, 6 October 2008: 9:00 AM
George R. Brown Convention Center, General Assembly Theater Hall B

Ryan L. Fimmen, Battelle - Environmental Restoration, Columbus, OH and Daniel Richter, Nicholas School of Environment and Earth Sciences, Duke University, Durham, NC
Abstract:
Field-scale observations of two upland soils derived from contrasting granite and basalt bedrocks are presented to hypothesize that redox activity of rhizospheres exerts substantial effects on mineral dissolution and colloidal translocation in many upland soils. Rhizospheres are redox-active microsites and in the absence of O2, oxidation of rhizodeposits can be coupled by reduction of redoxactive species such as Fe, a biogenic reduction that leads to Fe translocation and oxidation, accompanied by substantial proton flux. Not only do rhizogenic Fe–C redox cycles demonstrate a process by which the rhizosphere affects an environment well outside the near-root zone, but these redox processes are also hypothesized to be potent weathering systems, such that rhizogenic redox-reactions complement acid- and ligand-promoted reactions as major biogeochemical processes that control crustal weathering. The potential significance of Fe–C redox cycling is underscored by the deep and extensive rooting and mottling of upland subsoils across a wide range of plant communities, lithologies, and soil-moisture and temperature regimes.

See more from this Division: Joint Sessions
See more from this Session: Soils through Time: Critical Zone Studies of Processes and Their Effects