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Nakagawa, Fumiko; Yoshida, Naohiro; Sugimoto, Akihiro; Wada, Eitaro; Yoshioka, Takahito; Ueda, Seinosuke; Vijarnsorn, Pisoot

doi:10.1023/a:1020270032512

Cited by 45 publications

(21 citation statements)

References 55 publications

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“…This indicates a greater role for temperature than GPP in driving seasonal CH 4 dynamics in these Mediterranean and nutrientrich wetlands. This stands in contrast with previously studied peatlands (e.g., Wahlen et al, 2006;Chanton et al, 1995;Martens et al, 1992;Nakagawa et al, 2002, in Schuur et al, 2016 where fresh C supply is thought to be strongly limiting.…”

Section: Seasonality and Sensitivity To Short-term Temperature Changecontrasting

confidence: 94%

“…Observations of wetland Δ 14 CH 4 have generally displayed modern signatures from which it has been inferred that recently fixed photosynthetic C substrates dominate wetland methanogenesis (e.g., Chanton et al, 1995Chanton et al, , 2008Martens, Kelley, Chanton, & Showers, 1992;Nakagawa et al, 2002;Schuur et al, 2016;Wahlen et al, 2006). In this study of a reflooded peatland, 14 C signatures for CH 4 were among the oldest that have been observed from within wetlands, except for thawing permafrost where very old peat can be relatively shallow (Estop-Aragonés et al, 2018).…”

Section: Provenance Of Ch 4 Productionmentioning

confidence: 55%

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Where old meets new: An ecosystem study of methanogenesis in a reflooded agricultural peatland

McNicol

Knox

Guilderson

et al. 2019

Global Change Biology

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Reflooding formerly drained peatlands has been proposed as a means to reduce losses of organic matter and sequester soil carbon for climate change mitigation, but a renewal of high methane emissions has been reported for these ecosystems, offsetting mitigation potential. Our ability to interpret observed methane fluxes in reflooded peatlands and make predictions about future flux trends is limited due to a lack of detailed studies of methanogenic processes. In this study we investigate methanogenesis in a reflooded agricultural peatland in the Sacramento Delta, California. We use the stable‐and radio‐carbon isotopic signatures of wetland sediment methane, ecosystem‐scale eddy covariance flux observations, and laboratory incubation experiments, to identify which carbon sources and methanogenic production pathways fuel methanogenesis and how these processes are affected by vegetation and seasonality. We found that the old peat contribution to annual methane emissions was large (~30%) compared to intact wetlands, indicating a biogeochemical legacy of drainage. However, fresh carbon and the acetoclastic pathway still accounted for the majority of methanogenesis throughout the year. Although temperature sensitivities for bulk peat methanogenesis were similar between open‐water (Q10 = 2.1) and vegetated (Q10 = 2.3) soils, methane production from both fresh and old carbon sources showed pronounced seasonality in vegetated zones. We conclude that high methane emissions in restored wetlands constitute a biogeochemical trade‐off with contemporary carbon uptake, given that methane efflux is fueled primarily by fresh carbon inputs.

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Section: Seasonality and Sensitivity To Short-term Temperature Changecontrasting

confidence: 94%

Section: Provenance Of Ch 4 Productionmentioning

confidence: 55%

Where old meets new: An ecosystem study of methanogenesis in a reflooded agricultural peatland

McNicol

Knox

Guilderson

et al. 2019

Global Change Biology

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“…The Δ 14 C of biogenic CH 4 emissions, Δ b , for recently assimilated organic material that is the substrate for CH 4 from livestock, rice paddies, and landfills will be similar to atmospheric Δ 14 CO 2 , approximately 20‰ in 2014 (Graven et al, 2017). For CH 4 produced from older organic material Δ b may be higher or lower, depending on the age of the organic material (Chanton et al, 1995;Garnett et al, 2013;Nakagawa et al, 2002). Materials aged on the order of decades would have higher Δ b due to nuclear weapons testing and the subsequent decline in Δ 14 CO 2 , whereas materials aged over centuries or millennia would have lower Δ b due to radioactive decay.…”

Section: 1029/2018ef001064mentioning

confidence: 99%

Detection of Fossil and Biogenic Methane at Regional Scales Using Atmospheric Radiocarbon

2019

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Regional emissions of methane and their attribution to a variety of sources presently have large uncertainties. Measurements of radiocarbon ( 14 C) in methane (CH 4 ) may provide a method for identifying regional CH 4 emissions from fossil versus biogenic sources because adding 14 C‐free fossil carbon reduces the 14 C/C ratio (Δ 14 CH 4 ) in atmospheric CH 4 much more than biogenic carbon does. We describe an approach for estimating fossil and biogenic CH 4 at regional scales using atmospheric Δ 14 CH 4 observations. As a case study to demonstrate expected Δ 14 CH 4 and Δ 14 CH 4 ‐CH 4 relationships, we simulate and compare Δ 14 CH 4 at a network of sites in California using two gridded CH 4 emissions estimates (Emissions Database for Global Atmospheric Research, EDGAR, and Gridded Environmental Protection Agency, GEPA) and the CarbonTracker‐Lagrange model for 2014, and for 2030 under business‐as‐usual and mitigation scenarios. The fossil fraction of CH 4 (F) is closely linked with the simulated Δ 14 CH 4 ‐CH 4 slope and differences of 2–21% in median F are found for EDGAR versus GEPA in 2014, and 7–10% for business‐as‐usual and mitigation scenarios in 2030. Differences of 10% in F for >200 ppb of added CH 4 produce differences of >10‰ in Δ 14 CH 4 , which are likely detectable from regular observations. Nuclear power plant 14 CH 4 emissions generally have small simulated median influences on Δ 14 CH 4 (0–7‰), but under certain atmospheric conditions they can be much stronger (>30‰) suggesting they must be considered in applications of Δ 14 CH 4 in California. This study suggests that atmospheric Δ 14 CH 4 measurements could provide powerful constraints on regional CH 4 emissions, complementary to other monitoring techniques.

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“…Integral to these estimates for the strength of peatlands as C sinks are the rates of CH 4 emission accompanying CO 2 sequestration [Whiting and Chanton, 2001]. Methane has a global warming potential that is 28 times higher than that of CO 2 over a 100 year time horizon [Myhre et al, 2013]. Wetlands emit between 80 and 280 Tg CH 4 yr À1 or about one third of global emissions, with much of this (47 to 89%) attributed to tropical wetlands [Bloom et al, 2010;Bridgham et al, 2013].…”

Section: Introductionmentioning

confidence: 99%

“…In the Florida Everglades, a subtropical minerotrophic wetland (pH~8), CH 4 was produced mainly via AM, but the proportion of HM increased along an increasing nutrient gradient . Between 52 and 73% of the CH 4 produced in peat soil in a swamp in Thailand was from HM [Nakagawa et al, 2002] (pH unknown), and HM was responsible for >50% of the CH 4 production in tropical lake (pH 6.3-7.7) sediments in Brazil [Conrad et al, 2011].…”

Section: Introductionmentioning

confidence: 99%

CO₂ and CH₄ isotope compositions and production pathways in a tropical peatland

Holmes

Chanton

Tfaily

et al. 2015

Global Biogeochemical Cycles

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While it is widely recognized that peatlands are important in the global carbon cycle, there is limited information on belowground gas production in tropical peatlands. We measured pore water methane (CH 4 ) and carbon dioxide (CO 2 ) concentrations and δ 13 C isotopic composition and CH 4 and CO 2 production rates in peat incubations from the Changuinola wetland in Panama. Our most striking finding was that CH 4 was depleted in 13 C (À94‰ in pore water and produced at À107‰ in incubated peat) relative to CH 4 found in most temperate and northern wetlands, potentially impacting the accuracy of approaches that use carbon isotopes to constrain global mass balance estimates. Fractionation factors between CH 4 and CO 2 showed that hydrogenotrophic methanogenesis was the dominant CH 4 production pathway, with up to 100% of the CH 4 produced via this route. Far more CO 2 than CH 4 (7 to 100X) was measured in pore water, due in part to loss of CH 4 through ebullition or oxidation and to the production of CO 2 from pathways other than methanogenesis. We analyzed data on 58 wetlands from the literature to determine the dominant factors influencing the relative proportions of CH 4 produced by hydrogenotrophic and acetoclastic methanogenesis and found that a combination of environmental parameters including pH, vegetation type, nutrient status, and latitude are correlated to the dominant methanogenic pathway. Methane production pathways in tropical peatlands do not correlate with these variables in the same way as their more northerly counterparts and thus may be differently affected by climate change.

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Cited by 45 publications

References 55 publications

Where old meets new: An ecosystem study of methanogenesis in a reflooded agricultural peatland

Where old meets new: An ecosystem study of methanogenesis in a reflooded agricultural peatland

Detection of Fossil and Biogenic Methane at Regional Scales Using Atmospheric Radiocarbon

CO₂ and CH₄ isotope compositions and production pathways in a tropical peatland

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Untitled

Cited by 45 publications

References 55 publications

Where old meets new: An ecosystem study of methanogenesis in a reflooded agricultural peatland

Where old meets new: An ecosystem study of methanogenesis in a reflooded agricultural peatland

Detection of Fossil and Biogenic Methane at Regional Scales Using Atmospheric Radiocarbon

CO2 and CH4 isotope compositions and production pathways in a tropical peatland

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CO₂ and CH₄ isotope compositions and production pathways in a tropical peatland