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Final Published Version
Author
Olshansky, YanivKnowles, John F.
Barron‐Gafford, Greg A.
Rasmussen, Craig
Abramson, Nate
Chorover, Jon
Affiliation
Univ Arizona, Dept Soil Water & Environm SciUniv Arizona, Sch Geog & Dev
Univ Arizona, Biosphere 2
Issue Date
2019-09-09
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AMER GEOPHYSICAL UNIONCitation
Olshansky, Y., Knowles, J. F., Barron‐Gafford, G. A., Rasmussen, C., Abramson, N., & Chorover, J. (2019). Soil fluid biogeochemical response to climatic events. Journal of Geophysical Research: Biogeosciences,124,2866–2882. https://doi.org/10.1029/2019JG005216Rights
Copyright © 2019. The Authors. This is an open access article under the terms of the Creative Commons Attribution License.Collection Information
This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.Abstract
Predicting fluid biogeochemistry in the vadose zone is difficult because of time‐dependent variation in multiple controlling factors, such as temperature, moisture, and biological activity. Furthermore, soils are multicomponent, heterogeneous porous media where manifold reactions may be affecting solution chemistry. We postulated that ecosystem‐scale processes, such as carbon fixation and ecohydrologic partitioning, control subsurface biogeochemical reactions, including mineral weathering. To test this hypothesis, we applied a novel “instrumented pedon” research approach. Analysis of the data streams demonstrates the interactions between pulsed wetting events and biogeochemical processes in the soil profile, and along groundwater flow paths. Rapid wetting front propagation into dry soil resulted in a pulsed increase in CO2 partial pressure in deeper soil layers, whereas wetting front propagation into a premoistened soil profile showed the opposite effect. The apparent respiratory quotient (ARQ), calculated from CO2 and O2 fluxes, deviated from expected oxidative ratios particularly during soil wetting events. These deviations were correlated in time with pore water geochemical responses, revealing that a fraction of the respired CO2 was consumed locally in pulsed silicate weathering events that accompanied wetting‐front propagation. However, most of this CO2 was dissolved in the soil pore water and transported downgradient, and along the soil‐bedrock interface, where a portion of it was further consumed in silicate weathering reactions, and another portion was degassed to the atmosphere. These results highlight the tight coupling that exists between physical, biological, and chemical processes, on event time scales, during incremental co‐evolution of the critical zone, particularly in water‐limited systems.Note
Open access articleISSN
2169-8953Version
Final published versionSponsors
National Science Foundation (NSF) [EAR-1331408]; Catalina-Jemez Critical Zone Observatory; Binational Agricultural Research and Development (BARD) program [FI-534-2015]ae974a485f413a2113503eed53cd6c53
10.1029/2019jg005216
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Except where otherwise noted, this item's license is described as Copyright © 2019. The Authors. This is an open access article under the terms of the Creative Commons Attribution License.