Lba-Eco Lc-07 Monthly Mean Flooded Wetlands Habitat, Central Amazon Basin: 1979-1996

Mélack, John M.; Hess, L.; Gastil-Buhl, M.; Forsberg, B.R.; Hamilton, Stephen K.; Lima, I.B.T.; Novo, Evlyn Márcia Leão de Moraes

doi:10.3334/ornldaac/1049

Cited by 1 publication

(1 citation statement)

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“…To estimate total annual CH4 contributions from the entire lowland Amazon basin, we averaged CH4 emissions across 13 sites for each individual pathways studied, assumed the estimated fluxes are representative of basin-wide fluxes and then applied the fluxes to the entire Amazon basin area, which was estimated using surface area data obtained from Melack et al 34 and Hess et al 22 (Supplementary Table 5). Monthly area coverage for open water, flooded forest and macrophytes in 1.77 million km 2 of the central Amazon basin were obtained from Melack et al and the percentage decrease in water-table depths relative to October data (lowest water-table month reported for most land cover classes by Melack et al ) and percentage increase in water-table depths relative to May data (highest water-table month reported for most land cover classes in Melack et al 34 ) was estimated. The percentage increases/decreases were applied to the high and low water surface area for flooded forest, open water and macrophyte area within the Amazon basin wetland area (8.4 × 10 5 km 2 ) reported in Hess et al 22 and surface areas for the remaining months were estimated.…”

Section: Ecosystem Scale Measurementsmentioning

confidence: 99%

Large emissions from floodplain trees close the Amazon methane budget

Pangala

Enrich‐Prast

Basso

et al. 2017

Nature

238

272

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Wetlands are the largest global source of atmospheric methane (CH), a potent greenhouse gas. However, methane emission inventories from the Amazon floodplain, the largest natural geographic source of CH in the tropics, consistently underestimate the atmospheric burden of CH determined via remote sensing and inversion modelling, pointing to a major gap in our understanding of the contribution of these ecosystems to CH emissions. Here we report CH 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 CH emissions. Methane fluxes from Amazon tree stems were up to 200 times larger than emissions reported for temperate wet forests and tropical peat swamp forests, representing the largest non-ebullitive wetland fluxes observed. Emissions from trees had an average stable carbon isotope value (δC) 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 CH a year, in addition to the 20.5 ± 5.3 teragrams a year emitted regionally from other sources. Furthermore, we provide a 'top-down' regional estimate of CH emissions of 42.7 ± 5.6 teragrams of CH a year for the Amazon basin, based on regular vertical lower-troposphere CH profiles covering the period 2010-2013. We find close agreement between our 'top-down' and combined 'bottom-up' estimates, indicating that large CH emissions from trees adapted to permanent or seasonal inundation can account for the emission source that is required to close the Amazon CH budget. Our findings demonstrate the importance of tree stem surfaces in mediating approximately half of all wetland CH emissions in the Amazon floodplain, a region that represents up to one-third of the global wetland CH source when trees are combined with other emission sources.

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