TY - JOUR
T1 - Theoretical Constraints on Fe Reduction Rates in Upland Soils as a Function of Hydroclimatic Conditions
AU - Calabrese, Salvatore
AU - Barcellos, Diego
AU - Thompson, Aaron
AU - Porporato, Amilcare
N1 - Funding Information:
We thank the anonymous reviewers for their constructive comments. This work was supported by the Department of Biological and Agricultural Engineering and AgriLife Research at Texas A&M University, the USDA National Institute of Food and Agriculture Hatch project 1023954, the National Science Foundation (NSF) Grants EAR‐1331846, FESD‐1338694, EAR‐1331841, and DEB‐1457761, and the Carbon Mitigation Initiative at Princeton University.
Funding Information:
We thank the anonymous reviewers for their constructive comments. This work was supported by the Department of Biological and Agricultural Engineering and AgriLife Research at Texas A&M University, the USDA National Institute of Food and Agriculture Hatch project 1023954, the National Science Foundation (NSF) Grants EAR-1331846, FESD-1338694, EAR-1331841, and DEB-1457761, and the Carbon Mitigation Initiative at Princeton University.
Publisher Copyright:
©2020. American Geophysical Union. All Rights Reserved.
PY - 2020/12
Y1 - 2020/12
N2 - Periods of high soil wetness promote anaerobic processes such as iron (Fe) reduction within soil microsites, with implications for organic matter decomposition, the fate of pollutants, and nutrient cycling. Here we discuss potential Fe reduction rates emerging from an interplay between the timescales of the internal reactions (Fe oxidation and reduction) and external forcings (length of oxic vs. anoxic conditions), and under no organic substrate and microbial population limitations. We compute the upper bound on Fe reduction and the theoretical maximum reduction rate, which would be reached under “resonant conditions,” whereby the timescales of external forcings match the internal timescales of the redox reactions. The variability of soil oxygen is then linked to rainfall frequency and intensity through soil moisture dynamics, allowing us to determine the hydroclimatic conditions that generate oxic/anoxic cycles that most favor Fe reduction. These predictions are applied to an aseasonal tropical (Luquillo, Puerto Rico, USA) and a seasonal subtropical (Calhoun, SC, USA) humid forests. We show that the tropical site maintains a high potential for Fe reduction throughout the year, due to rapid and frequent transitions between predicted oxic and anoxic microsite conditions, with a potential to reduce up to 1,800 mmol kg−1 soil of Fe per year, while a less humid and seasonal climate in the subtropical site limits maximum reduction rates to 60 mmol kg−1 year−1. This analysis paves the way for a global identification of hot spots of potential Fe reduction using readily available hydroclimatic observations.
AB - Periods of high soil wetness promote anaerobic processes such as iron (Fe) reduction within soil microsites, with implications for organic matter decomposition, the fate of pollutants, and nutrient cycling. Here we discuss potential Fe reduction rates emerging from an interplay between the timescales of the internal reactions (Fe oxidation and reduction) and external forcings (length of oxic vs. anoxic conditions), and under no organic substrate and microbial population limitations. We compute the upper bound on Fe reduction and the theoretical maximum reduction rate, which would be reached under “resonant conditions,” whereby the timescales of external forcings match the internal timescales of the redox reactions. The variability of soil oxygen is then linked to rainfall frequency and intensity through soil moisture dynamics, allowing us to determine the hydroclimatic conditions that generate oxic/anoxic cycles that most favor Fe reduction. These predictions are applied to an aseasonal tropical (Luquillo, Puerto Rico, USA) and a seasonal subtropical (Calhoun, SC, USA) humid forests. We show that the tropical site maintains a high potential for Fe reduction throughout the year, due to rapid and frequent transitions between predicted oxic and anoxic microsite conditions, with a potential to reduce up to 1,800 mmol kg−1 soil of Fe per year, while a less humid and seasonal climate in the subtropical site limits maximum reduction rates to 60 mmol kg−1 year−1. This analysis paves the way for a global identification of hot spots of potential Fe reduction using readily available hydroclimatic observations.
KW - carbon cycle
KW - iron redox model
KW - iron reduction
KW - soil iron redox
KW - soil moisture control
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U2 - 10.1029/2020JG005894
DO - 10.1029/2020JG005894
M3 - Article
AN - SCOPUS:85097996984
SN - 2169-8953
VL - 125
JO - Journal of Geophysical Research: Biogeosciences
JF - Journal of Geophysical Research: Biogeosciences
IS - 12
M1 - e2020JG005894
ER -