Atmospheric nitrous oxide (N2O) is a potent greenhouse gas thought to be mainly derived from microbial metabolism as part of the denitrification pathway. Here we report that in unexplored peat soils of Central and South America, N2O production can be driven by abiotic reactions (≤98%) highly competitive to their enzymatic counterparts. Extracted soil iron positively correlated with in situ abiotic N2O production determined by isotopic tracers. Moreover, we found that microbial N2O reduction accompanied abiotic production, essentially closing a coupled abiotic-biotic N2O cycle. Anaerobic N2O consumption occurred ubiquitously (pH 6.4–3.7), with proportions of diverse clade II N2O reducers increasing with consumption rates. Our findings show that denitrification in tropical peat soils is not a purely biological process but rather a ‘mosaic’ of abiotic and biotic reduction reactions. We predict that hydrological and temperature fluctuations differentially affect abiotic and biotic drivers and further contribute to the high N2O flux variation in the region.
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All data to evaluate the conclusions of the study are present in the paper and its Supplementary Information and can be found in the Figshare repository (https://doi.org/10.6084/m9.figshare.19552588.v1). Genomic data have been deposited in the GenBank, EMBL, and DDBJ databases under accession: SAMN27959396, SAMN27959397, SAMN27959398, SAMN27959399, SAMN27959400, SAMN27959401, SAMN27959402, SAMN27959403, SAMN27959404, SAMN27959405, SAMN27959406, SAMN27959407, SAMN27959408, SAMN27959409, SAMN27959410, SAMN27959411, SAMN27959412, SAMN27959413, SAMN27959414, SAMN27959415, SAMN27959416, SAMN27959417, SAMN27959418, SAMN27959419, SAMN27959420, SAMN27959421, SAMN27959422, SAMN27959423, SAMN27959424, SAMN27959425, SAMN27959426, SAMN27959427, SAMN27959428, SAMN27959429, SAMN27959430, SAMN27959431, SAMN27959432, SAMN27959433, SAMN27959434, SAMN27959435, SAMN27959436, SAMN27959437, SAMN27959438, SAMN27959439, SAMN27959440, SAMN27959441, SAMN27959442 and SAMN27959443
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We acknowledge R. T. Espinoza, T. P. Gomez, D. Reyna, B. Crnobrna, O. Lähteenoja, K. Arbaiza, A. H. Carmona, P. Fonteboa, R. C. Chaves, J. R. Trucios, C. M. Cadillo-Quiroz, the UFSJ Graduate Program in Geography (PPGEOG) and the Office for International Affairs (ASSIN/UFSJ) for assistance and help during stages of field work. We also thank W. Nitschke (CNRS/BIP) for discussions, M. Abdalla for efforts supporting this effort at the USAID-GDR program at ASU, and the USAID missions in Peru and Brazil.
This study was funded by an NSF-DEB award (no. 1355066) and a SOLS -KED ASU award (ECR A548 HC) to H.C-Q, a Global Development Research Scholarship to S.B. and H.C-Q in partnership with the USAID-Global Development Lab and the Peruvian and Brazilian USAID missions. S.B. also received support from the Lewis & Clark Fund for Exploration and Field Research in Astrobiology provided by the American Philosophical Society (APS). N.E.O. was funded in part by the DOE Great Lakes Bioenergy Research Center (DOE BER Office of Science DE-SC0018409).
The authors declare no competing interests.
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This workflow was applied for each peatland. Derived data sets are in circles. At the end of the incubations, microcosms were opened, and soil dry mass was determined for each replicate in order to normalize rates. Headspace of lab incubations was sporadically tested for CO2 accumulation to verify absence of biological activity.
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Buessecker, S., Sarno, A.F., Reynolds, M.C. et al. Coupled abiotic-biotic cycling of nitrous oxide in tropical peatlands. Nat Ecol Evol 6, 1881–1890 (2022). https://doi.org/10.1038/s41559-022-01892-y