DOE OSTI · 2530936
Duration of O 2 Exposure Determines Dominance of Fe II vs CH 4 Production in Tropical Forest Soils
Abstract
Temporal fluctuations in redox conditions influence the availability of Fe III and greenhouse gas emissions in humid upland soils. However, the impact of fluctuation duration on biogeochemical processes remains unclear. We hypothesized that rates of Fe III reduction and CH 4 production are sensitive to the duration of soil oxygenation. To test this, surface soil from the Luquillo Forest, Puerto Rico, was subjected to fluctuating redox conditions with an anoxic interval of 6 days followed by oxic intervals of either 8, 24, or 72 h. Shorter oxic intervals enhanced Fe reduction, while longer oxic intervals enhanced CH 4 emissions. As O 2 exposure decreased from 72 to 8 h, Fe reduction rates increased from 0.12 ± 0.02 to 0.26 ± 0.05 mmol kg –1 h –1 , whereas cumulative CH 4 decreased from 44.0 ± 4.7 to 12.7 ± 4.6 μmol kg –1 . 13 C-amino acid spikes were preferentially incorporated into the DNA of iron reducers (Anaeromyxobacter sp.) in the shorter oxic treatment (8 h vs 24 h), suggesting that Fe reducers are less inhibited by shorter periods of oxidation. Conversely, longer oxygen pulses appear to suppress Fe reducers more than methanogens, leading to increased CH 4 emissions. These findings highlight the role of the redox oscillation length in modulating biogeochemical processes and greenhouse gas emissions in soils.
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Barcellos, Diego [University of Georgia, Athens, GA (United States); Federal University of São Paulo (UNIFESP), Sao Paulo (Brazil)] (ORCID:0000000241982843), Castro, Sherlynette Pérez [University of Georgia, Athens, GA (United States)] (ORCID:0000000222570966), Campbell, Ashley [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); Adaptive Biotechnologies, Seattle, WA (United States)] (ORCID:0000000222538317), Kimbrel, Jeffrey A. [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0000000172139392), Blazewicz, Steven Joseph [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0000000175171750), Wollard, Jessica [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0000000293292609), Pett-Ridge, Jennifer [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); University of California, Merced, CA (United States); University of California, Berkeley, CA (United States)] (ORCID:0000000244392398), Thompson, Aaron [University of Georgia, Athens, GA (United States)] (ORCID:0000000163017377). 2025-02-28. Duration of O 2 Exposure Determines Dominance of Fe II vs CH 4 Production in Tropical Forest Soils. https://doi.org/10.1021/acs.est.4c12329
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