Tradeoff of CO2 and CH4 emissions from global peatlands under water-table drawdown

Huang, Yuanyuan; Ciais, P.; Luo, Yiqi; Zhu, Dan; Wang, Ying‐Ping; Qiu, Chunjing; Goll, Daniel S.; Guenet, Bertrand; Makowski, David; Graaf, Inge de; Leifeld, Jens; Kwon, Mi Hye; Hu, Jing; Qu, Laiye

doi:10.1038/s41558-021-01059-w

Cited by 98 publications

(90 citation statements)

References 38 publications

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“…They suggest in fact, that lowering of the water table will increase CO 2 emission rates from peatlands and might further compromise their carbon balance. All this is coherent with the enhancement in GHG emissions, only partly offset by inhibition of methanogenesis, that was recently predicted through a machine learning upscaling approach by Huang et al [23].…”

Section: Discussionsupporting

confidence: 82%

“…The greater incidence and length of drought periods fostered by climate change will cause a more and more frequent onset of aerobic conditions in thicker sections of peat deposit profiles [21,22]. Impacts of water table lowering on GHG emissions from peatlands are highly variable: most studies report reductions in CH 4 emissions, although the overall balance foresees a net increase from 0.73 to 0.86 Gt CO 2 -eq yr −1 by the end of the century [23]. The factors that affect the mechanisms underlying this variability have not been fully elucidated yet, but HA certainly play a pivotal role [19].…”

Section: Introductionmentioning

confidence: 99%

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Electrochemical and Structural Modifications of Humic Acids in Aerobically and Anaerobically Incubated Peat

Bravo¹,

Toniolo²,

Contin³

et al. 2021

Land

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Exposure to oxygen and aerobic biological activity during drought periods alters the availability of terminal electron acceptors (TEA) in the peat catotelm layer. We investigated the changes in the electrochemical and chemical characteristics of humic acids (HA) induced by subjecting air-dried sphagnum peat to biological oxidation or reduction during a 90-day incubation experiment. Structural modifications of HAs from anaerobically (HAred) and aerobically (HAox) incubated peat were investigated by ATR-FTIR, UV–vis, and EEM fluorescence spectroscopy. Number and strength of acid groups were characterized by titration, while changes in redox properties were characterized by cyclic voltammetry and quantified by coulometry with mediated electrochemical oxidation (MEO). Exposure to oxygen had small effects, but compared to anaerobic incubation, decreased by 20% the capacity of HA to reduce the radical ion of 2,2′-Azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS●−), passing from 2.77 ± 0.13 mmole- gHA−1 in HAred to 2.21 ± 0.10 mmole- gHA−1 in HAox. Pseudo-first-order electron transfer kinetic constants were 13.3 ± 1.2 s−1 for HAox and 16.7 ± 1.4 s−1 for HAred. Alterations in the hydrological status of the catotelm have minor effects on the actual in situ availability of organic TEA, but if coupled to intensified biological activity they may result in significant variations of greenhouse gases emissions.

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Section: Discussionsupporting

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Electrochemical and Structural Modifications of Humic Acids in Aerobically and Anaerobically Incubated Peat

Bravo¹,

Toniolo²,

Contin³

et al. 2021

Land

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“…Carbon dioxide, methane, and nitrous oxide can be significant contributors to greenhouse gas emissions from wetlands (5) especially from disturbances that liberate previously stabilized carbon e.g. (6)(7)(8)(9)(10).…”

Section: Introductionmentioning

confidence: 99%

Improved Wetland Soil Organic Carbon Stocks of the Conterminous U.S. Through Data Harmonization

et al. 2021

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Wetland soil stocks are important global repositories of carbon (C) but are difficult to quantify and model due to varying sampling protocols, and geomorphic/spatio-temporal discontinuity. Merging scales of soil-survey spatial extents with wetland-specific point-based data offers an explicit, empirical and updatable improvement for regional and continental scale soil C stock assessments. Agency-collected and community-contributed soil datasets were compared for representativeness and bias, with the goal of producing a harmonized national map of wetland soil C stocks with error quantification for wetland areas of the conterminous United States (CONUS) identified by the USGS National Landcover Change Dataset. This allowed an empirical predictive model of SOC density to be applied across the entire CONUS using relational %OC distribution alone. A broken-stick quantile-regression model identified %OC with its relatively high analytical confidence as a key predictor of SOC density in soil segments; soils <6% OC (hereafter, mineral wetland soils, 85% of the dataset) had a strong linear relationship of %OC to SOC density (RMSE = 0.0059, ~4% mean RMSE) and soils >6% OC (organic wetland soils, 15% of the dataset) had virtually no predictive relationship of %OC to SOC density (RMSE = 0.0348 g C cm−3, ~56% mean RMSE). Disaggregation by vegetation type or region did not alter the breakpoint significantly (6% OC) and did not improve model accuracies for inland and tidal wetlands. Similarly, SOC stocks in tidal wetlands were related to %OC, but without a mappable product for disaggregation to improve accuracy by soil class, region or depth. Our layered harmonized CONUS wetland soil maps revised wetland SOC stock estimates downward by 24% (9.5 vs. 12.5Pg C) with the overestimation being entirely an issue of inland organic wetland soils (35% lower than SSURGO-derived SOC stocks). Further, SSURGO underestimated soil carbon stocks at depth, as modeled wetland SOC stocks for organic-rich soils showed significant preservation downcore in the NWCA dataset (<3% loss between 0 and 30 cm and 30 and 100 cm depths) in contrast to mineral-rich soils (37% downcore stock loss). Future CONUS wetland soil C assessments will benefit from focused attention on improved organic wetland soil measurements, land history, and spatial representativeness.

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“…These shifts may provide optimal conditions for CH4 production and emissions, particularly in the initial decades following thaw. Peatland CH4 emissions are constrained by the water table position (Huang et al, 2021;Strack et al, 2004), and surface inundation leads to increased CH4 emissions (Tuittila et al, 2000). Methane production and emissions are positively influenced by soil temperatures (Hopple et al, 2020;Olefeldt et al, 2017), and peatland CH4 emissions have been shown to increase when both the water table position and temperatures are high (Grant, 2015).…”

Section: Introductionmentioning

confidence: 99%

High peatland methane emissions following permafrost thaw: enhanced acetoclastic methanogenesis during early successional stages

Heffernan

Cavaco

Bhatia

et al. 2022

Preprint

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Abstract. Permafrost thaw in northern peatlands often leads to increased methane (CH4) emissions, but gaps remain in our understanding of the underlying controls responsible for increased emissions and the duration for which they persist. We assessed how shifting ecological conditions affect microbial communities, and the magnitude and stable isotopic signature (δ13C) of CH4 emissions along a thermokarst bog transect in boreal western Canada. Thermokarst bogs develop following permafrost thaw when dry, elevated peat plateaus collapse and become saturated and dominated by Sphagnum mosses. We differentiated between a young and a mature thermokarst bog stage (~30 and years ~200 since thaw, respectively). The young bog located along the thermokarst edge, was wetter, warmer and dominated by hydrophilic vegetation compared to the mature bog. Using 16S rRNA gene high throughput sequencing, we show that microbial communities were distinct near the surface and converged with depth, but lesser differences remained down to the lowest depth (160 cm). Microbial community analysis and δ13C data from CH4 surface emissions and dissolved gas depth profiles show that hydrogenotrophic methanogenesis was the dominant pathway at both sites. However, the young bog was found to have isotopically heavier δ13C-CH4 in both dissolved gases profiles and surface CH4 emissions, suggesting that acetoclastic methanogenesis was relatively more enhanced throughout the young bog peat profile. Furthermore, young bog CH4 emissions were three times greater than the mature bog. Our study suggests that interactions between ecological conditions and methanogenic communities enhance CH4 emissions in young thermokarst bogs, but these favorable conditions only persist for the initial decades after permafrost thaw.

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Tradeoff of CO2 and CH4 emissions from global peatlands under water-table drawdown

Cited by 98 publications

References 38 publications

Electrochemical and Structural Modifications of Humic Acids in Aerobically and Anaerobically Incubated Peat

Electrochemical and Structural Modifications of Humic Acids in Aerobically and Anaerobically Incubated Peat

Improved Wetland Soil Organic Carbon Stocks of the Conterminous U.S. Through Data Harmonization

High peatland methane emissions following permafrost thaw: enhanced acetoclastic methanogenesis during early successional stages

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