Large emissions from floodplain trees close the Amazon methane budget

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Pangala, Sunitha R. ^{[1, 2]} ; Enrich-Prast, Alex ^{[3, 4]} ; Basso, Luana S. ^[5] ; Peixoto, Roberta Bittencourt ^[3] ; Bastviken, David ^[4] ; Hornibrook, Edward R. C. ^{[6, 7]} ; Gatti, Luciana V. ^{[5, 8]} ; Marotta, Humberto ^{[9, 10]} ; Braucks Calazans, Luana Silva ^[3] ; Sakuragui, Cassia Monica ^[3] ; Bastos, Wanderley Rodrigues ^[11] ; Malm, Olaf ^[12] ; Gloor, Emanuel ^[13] ; Miller, John Bharat ^[14] ; Gauci, Vincent ^[2]

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^[1] Univ Lancaster, Lancaster Environm Ctr, Lancaster LA1 4YQ - England

^[2] Open Univ, Sch Environm Earth & Ecosyst Sci, Walton Hall, Milton Keynes MK7 6AA, Bucks - England

^[3] Univ Fed Rio de Janeiro, Inst Biol, Dept Bot, Rio De Janeiro - Brazil

^[4] Linkoping Univ, Dept Themat Studies, Environm Change, SE-58183 Linkoping - Sweden

^[5] IPEN, CNEN, Atmospher Chem Lab, 2242 Ave Prof Lineu Prestes, BR-05508000 Sao Paulo - Brazil

^[6] Univ Bristol, Sch Earth Sci, Wills Mem Bldg, Queens Rd, Bristol BS8 1RJ, Avon - England

^[7] Univ British Columbia, Dept Earth Environm & Geog Sci, Irving K Barber Sch Arts & Sci, Okanagan Campus, 1177 Res Rd, Kelowna, BC V1V 1V7 - Canada

^[8] Natl Inst Space Res INPE, Ctr Earth Syst Sci CCST, Greenhouse Gas Lab LaGEE, Av Dos Astronautas 1758, BR-12227010 Sao Jose Dos Campos - Brazil

^[9] Univ Fed Fluminense, Ecosyst & Global Change Lab LEMG UFF, Int Lab Global Change LINCGlobal, Biomass & Water Management Res Ctr NAB UFF, Ave Edmundo March, BR-24210310 Niteroi, RJ - Brazil

^[10] Univ Fed Fluminense, Sedimentary & Environm Proc Lab LAPSA UFF, Dept Geog, Ave Gen Milton Tavares de Souza, BR-24210346 Niteroi, RJ - Brazil

^[11] Fed Univ Rondonia, Environm Biogeochem Lab, Rondonia - Brazil

^[12] Univ Fed Rio de Janeiro, Biophys Inst, Radioisotopes Lab, Rio De Janeiro - Brazil

^[13] Univ Leeds, Sch Geog, Woodhouse Lane, Leeds LS9 2JT, W Yorkshire - England

^[14] NOAA, Earth Syst Res Lab, Global Monitoring Div, 325 Broadway, Boulder, CO 80305 - USA

• Tipo de documento: Artigo Científico
• Fonte: Nature; v. 552, n. 7684, p. 230+, DEC 14 2017.
• Citações Web of Science: 32

Resumo

Wetlands are the largest global source of atmospheric methane (CH4)(1), a potent greenhouse gas. However, methane emission inventories from the Amazon floodplain(2,3), the largest natural geographic source of CH4 in the tropics, consistently underestimate the atmospheric burden of CH4 determined via remote sensing and inversion modelling(4,5), pointing to a major gap in our understanding of the contribution of these ecosystems to CH4 emissions. Here we report CH4 fluxes from the stems of 2,357 individual Amazonian floodplain trees from 13 locations across the central Amazon basin. We find that escape of soil gas through wetland trees is the dominant source of regional CH4 emissions. Methane fluxes from Amazon tree stems were up to 200 times larger than emissions reported for temperate wet forests(6) and tropical peat swamp forests(7), representing the largest non-ebullitive wetland fluxes observed. Emissions from trees had an average stable carbon isotope value (delta C-13) of -66.2 +/- 6.4 per mil, consistent with a soil biogenic origin. We estimate that floodplain trees emit 15.1 +/- 1.8 to 21.2 +/- 2.5 teragrams of CH4 a year, in addition to the 20.5 +/- 5.3 teragrams a year emitted regionally from other sources. Furthermore, we provide a `topdown' regional estimate of CH4 emissions of 42.7 +/- 5.6 teragrams of CH4 a year for the Amazon basin, based on regular vertical lower-troposphere CH4 profiles covering the period 2010-2013. We find close agreement between our `top-down' and combined `bottom-up' estimates, indicating that large CH4 emissions from trees adapted to permanent or seasonal inundation can account for the emission source that is required to close the Amazon CH4 budget. Our findings demonstrate the importance of tree stem surfaces in mediating approximately half of all wetland CH4 emissions in the Amazon floodplain, a region that represents up to one-third of the global wetland CH4 source when trees are combined with other emission sources. (AU)

• Processo FAPESP: 08/58120-3 - Carbon tracker and water availability controls of land use and climate changes
• Beneficiário: Humberto Ribeiro da Rocha
• Linha de fomento: Auxílio à Pesquisa - Programa de Pesquisa sobre Mudanças Climáticas Globais - Temático
• Processo FAPESP: 11/51841-0 - UK/Brazil research network for an Amazonian Carbon Observatory
• Beneficiário: Luciana Vanni Gatti
• Linha de fomento: Auxílio à Pesquisa - Programa de Pesquisa sobre Mudanças Climáticas Globais - Regular