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1. Methylotrophy in the Mire: direct and indirect routes for methane production in thawing permafrost

   https://doi.org/10.1128/msystems.00698-23  

   Ellenbogen, Jared B ; Borton, Mikayla A ; McGivern, Bridget B ; Cronin, Dylan R ; Hoyt, David W ; Freire-Zapata, Viviana ; McCalley, Carmody K ; Varner, Ruth K ; Crill, Patrick M ; Wehr, Richard A ; et al ( January 2024 , mSystems)

   Hernandez, Marcela (Ed.)

   While wetlands are major sources of biogenic methane (CH₄), our understanding of resident microbial metabolism is incomplete, which compromises the prediction of CH₄emissions under ongoing climate change. Here, we employed genome-resolved multi-omics to expand our understanding of methanogenesis in the thawing permafrost peatland of Stordalen Mire in Arctic Sweden. In quadrupling the genomic representation of the site’s methanogens and examining their encoded metabolism, we revealed that nearly 20% of the metagenome-assembled genomes (MAGs) encoded the potential for methylotrophic methanogenesis. Further, 27% of the transcriptionally active methanogens expressed methylotrophic genes; forMethanosarcinalesandMethanobacterialesMAGs, these data indicated the use of methylated oxygen compounds (e.g., methanol), while forMethanomassiliicoccales, they primarily implicated methyl sulfides and methylamines. In addition to methanogenic methylotrophy, >1,700 bacterial MAGs across 19 phyla encoded anaerobic methylotrophic potential, with expression across 12 phyla. Metabolomic analyses revealed the presence of diverse methylated compounds in the Mire, including some known methylotrophic substrates. Active methylotrophy was observed across all stages of a permafrost thaw gradient in Stordalen, with the most frozen non-methanogenic palsa found to host bacterial methylotrophy and the partially thawed bog and fully thawed fen seen to house both methanogenic and bacterial methylotrophic activities. Methanogenesis across increasing permafrost thaw is thus revised from the sole dominance of hydrogenotrophic production and the appearance of acetoclastic at full thaw to consider the co-occurrence of methylotrophy throughout. Collectively, these findings indicate that methanogenic and bacterial methylotrophy may be an important and previously underappreciated component of carbon cycling and emissions in these rapidly changing wetland habitats.

   Wetlands are the biggest natural source of atmospheric methane (CH₄) emissions, yet we have an incomplete understanding of the suite of microbial metabolism that results in CH₄formation. Specifically, methanogenesis from methylated compounds is excluded from all ecosystem models used to predict wetland contributions to the global CH₄budget. Though recent studies have shown methylotrophic methanogenesis to be active across wetlands, the broad climatic importance of the metabolism remains critically understudied. Further, some methylotrophic bacteria are known to produce methanogenic by-products like acetate, increasing the complexity of the microbial methylotrophic metabolic network. Prior studies of Stordalen Mire have suggested that methylotrophic methanogenesis is irrelevantin situand have not emphasized the bacterial capacity for metabolism, both of which we countered in this study. The importance of our findings lies in the significant advancement toward unraveling the broader impact of methylotrophs in wetland methanogenesis and, consequently, their contribution to the terrestrial global carbon cycle.

    

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2. Assessing methane emissions for northern peatlands in ORCHIDEE-PEAT revision 7020

   https://doi.org/10.5194/gmd-15-2813-2022  

   Salmon, Elodie ; Jégou, Fabrice ; Guenet, Bertrand ; Jourdain, Line ; Qiu, Chunjing ; Bastrikov, Vladislav ; Guimbaud, Christophe ; Zhu, Dan ; Ciais, Philippe ; Peylin, Philippe ; et al ( January 2022 , Geoscientific Model Development)

   Abstract. In the global methane budget, the largest natural sourceis attributed to wetlands, which encompass all ecosystems composed ofwaterlogged or inundated ground, capable of methane production. Among them,northern peatlands that store large amounts of soil organic carbon have beenfunctioning, since the end of the last glaciation period, as long-termsources of methane (CH4) and are one of the most significant methanesources among wetlands. To reduce uncertainty of quantifying methane flux in theglobal methane budget, it is of significance to understand the underlyingprocesses for methane production and fluxes in northern peatlands. A methanemodel that features methane production and transport by plants, ebullitionprocess and diffusion in soil, oxidation to CO2, and CH4 fluxes tothe atmosphere has been embedded in the ORCHIDEE-PEAT land surface modelthat includes an explicit representation of northern peatlands.ORCHIDEE-PCH4 was calibrated and evaluated on 14 peatland sites distributedon both the Eurasian and American continents in the northern boreal andtemperate regions. Data assimilation approaches were employed to optimizedparameters at each site and at all sites simultaneously. Results show thatmethanogenesis is sensitive to temperature and substrate availability overthe top 75 cm of soil depth. Methane emissions estimated using single siteoptimization (SSO) of model parameters are underestimated by 9 g CH4 m−2 yr−1 on average (i.e., 50 % higher than the site average ofyearly methane emissions). While using the multi-site optimization (MSO),methane emissions are overestimated by 5 g CH4 m−2 yr−1 onaverage across all investigated sites (i.e., 37 % lower than the siteaverage of yearly methane emissions). 

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3. Evidence for glacial geological controls on the hydrology of Maine (USA) peatlands

   https://doi.org/10.1130/G46844.1  

   Chen, Xi ; Comas, Xavier ; Reeve, Andrew ; Slater, Lee ( May 2020 , Geology)

   null (Ed.)

   Abstract Freshwater pools commonly form eccentric crescent patterns in peatlands, an important atmospheric methane (CH4) source, and show an apparent spatial association with eskers in some deglaciated regions. However, the role of underlying permeable glacial deposits such as eskers in regulating hydrogeology, and perhaps even carbon cycling, in peatlands is rarely considered. In this study, ground-penetrating radar imaging and direct coring confirmed that clustered pools coincide with buried esker crests in contact with peat soil in Caribou Bog and Kanokolus Bog in Maine (USA). Hydraulic head and geochemical data combined with lidar indicate vertical water flow from shallow peat toward the permeable esker crests, suggesting enhanced downward transport of labile organic carbon that presumably accelerates rates of methanogenesis in deep peat. Eskers might therefore serve as proxies for enhanced CH4 production in deep peat, as supported by differences in dissolved CH4 profiles depending on proximity to pools. Geographic data compiled from multiple sources suggest that many peatlands with eccentric pools appear to be located proximal to esker systems in Maine and Fennoscandia. These geological factors may be important, previously unrecognized controls on water and the carbon cycle in peatlands. 

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4. Belowground plant allocation regulates rice methane emissions from degraded peat soils

   https://doi.org/10.1038/s41598-024-64616-1  

   Sriskandarajah, Nijanthini ; Wüst-Galley, Chloé ; Heller, Sandra ; Leifeld, Jens ; Määttä, Tiia ; Ouyang, Zutao ; Runkle, Benjamin_R K ; Schiedung, Marcus ; Schmidt, Michael_W I ; Tumber-Dávila, Shersingh Joseph ; et al ( December 2024 , Scientific Reports)

   Carbon-rich peat soils have been drained and used extensively for agriculture throughout human history, leading to significant losses of their soil carbon. One solution for rewetting degraded peat is wet crop cultivation. Crops such as rice, which can grow in water-saturated conditions, could enable agricultural production to be maintained whilst reducing CO₂and N₂O emissions from peat. However, wet rice cultivation can release considerable methane (CH₄). Water table and soil management strategies may enhance rice yield and minimize CH₄emissions, but they also influence plant biomass allocation strategies. It remains unclear how water and soil management influences rice allocation strategies and how changing plant allocation and associated traits, particularly belowground, influence CH₄-related processes. We examined belowground biomass (BGB), aboveground biomass (AGB), belowground:aboveground ratio (BGB:ABG), and a range of root traits (root length, root diameter, root volume, root area, and specific root length) under different soil and water treatments; and evaluated plant trait linkages to CH₄. Rice (Oryza sativaL.) was grown for six months in field mesocosms under high (saturated) or low water table treatments, and in either degraded peat soil or degraded peat covered with mineral soil. We found that BGB and BGB:AGB were lowest in water saturated conditions where mineral soil had been added to the peat, and highest in low-water table peat soils. Furthermore, CH₄and BGB were positively related, with BGB explaining 60% of the variation in CH₄but only under low water table conditions. Our results suggest that a mix of low water table and mineral soil addition could minimize belowground plant allocation in rice, which could further lower CH₄likely because root-derived carbon is a key substrate for methanogenesis. Minimizing root allocation, in conjunction with water and soil management, could be explored as a strategy for lowering CH₄emissions from wet rice cultivation in degraded peatlands.

    

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5. Fate of methane in canals draining tropical peatlands

   https://doi.org/10.1038/s41467-024-54063-x  

   Perryman, Clarice_R ; Bowen, Jennifer_C ; Shahan, Julie ; Silviani_PAB, Desi ; Dayanti, Erin ; Andriyani, Yulita ; Asyhari, Adibtya ; Gangga, Adi ; Novita, Nisa ; Anshari, Gusti_Z ; et al ( November 2024 , Nature Communications)

   Tropical wetlands and freshwaters are major contributors to the growing atmospheric methane (CH₄) burden. Extensive peatland drainage has lowered CH₄emissions from peat soils in Southeast Asia, but the canals draining these peatlands may be hotspots of CH₄emissions. Alternatively, CH₄oxidation (consumption) by methanotrophic microorganisms may attenuate emissions. Here, we used laboratory experiments and a synoptic survey of the isotopic composition of CH₄in 34 canals across West Kalimantan, Indonesia to quantify the proportion of CH₄that is consumed and therefore not emitted to the atmosphere. We find that CH₄oxidation mitigates 76.4 ± 12.0% of potential canal emissions, reducing emissions by ~70 mg CH₄m⁻²d⁻¹. Methane consumption also significantly impacts the stable isotopic fingerprint of canal CH₄emissions. As canals drain over 65% of peatlands in Southeast Asia, our results suggest that CH₄oxidation significantly influences landscape-scale CH₄emissions from these ecosystems.

    

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