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Tree stem methane emissions are regulated by site‐level biogeochemistry over species identity in Amazon floodplain forests.

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Title: Tree stem methane emissions are regulated by site‐level biogeochemistry over species identity in Amazon floodplain forests.
Authors: Blincow, Holly R.1 (AUTHOR) holly.blincow@cumbria.ac.uk, McNamara, Niall P.2 (AUTHOR), Elias, Dafydd M. O.2 (AUTHOR), Gomez, Carla1,3 (AUTHOR), Lamb, Jack4 (AUTHOR), Nunes de Sousa, Rodrigo1 (AUTHOR), Gris, Darlene5 (AUTHOR), Pequeno Reis, Leonardo5,6 (AUTHOR), Hoyt, Alison M.4 (AUTHOR), Pangala, Sunitha Rao1,3 (AUTHOR) s.pangala@imperial.ac.uk
Source: New Phytologist. Jul2026, Vol. 251 Issue 1, p179-190. 12p.
Subjects: Biogeochemistry, Pore fluids, Plant biomass, Greenhouse gas mitigation, Floodplain forests
Geographic Terms: Amazon River
Abstract (English): Summary: Tree stems in Amazonian floodplains emit substantial methane (CH4), yet controls on emission variability remain unclear. Emissions span orders of magnitude between várzea (nutrient‐rich) and igapó (nutrient‐poor) forests and among trees, suggesting controls beyond flooding.We tested whether site‐level biogeochemistry better explains stem CH4 variability than species identity by measuring emissions from two co‐occurring species with contrasting wood densities – Eschweilera coriacea and Hevea spruceana – across várzea and igapó forests. Emissions were paired with porewater chemistry (electrical conductivity, dissolved oxygen, dissolved CH4, and dissolved organic carbon), methane production potential (MPP), and root biomass.Stem CH4 emissions were significantly higher in várzea than in igapó, independent of species or stem height. Várzea porewaters displayed higher conductivity, dissolved CH4 and MPP, near‐neutral pH, and lower oxygen, with fine roots concentrated in the 0‐ to 50‐cm soil layer, indicating a shallow CH4 supply zone. Basal stem emissions in várzea correlated with shallow porewater chemistry and fine‐root biomass, whereas relationships in igapó were weak.These findings show that Amazonian floodplain stem CH4 emissions are governed by shallow site‐level biogeochemistry, rather than species identity alone and should be incorporated into basin‐scale CH4 budgets and process models to capture spatial variability. [ABSTRACT FROM AUTHOR]
Abstract (Portuguese): Resumo: Troncos de árvores nas planícies alagáveis amazônicas emitem quantidades substanciais de metano (CH4), mas os fatores que controlam essa variabilidade ainda são pouco compreendidos. As emissões variam amplamente entre florestas de várzea (ricas em nutrientes) e igapó (pobres em nutrientes), bem como entre árvores, sugerindo controles além do alagamento.Avaliamos se a biogeoquímica em nível de sítio explica melhor a variabilidade do CH4 emitido pelos troncos do que a identidade das espécies, medindo emissões de duas espécies coocorrentes com densidades de madeira contrastantes – Eschweilera coriacea e Hevea spruceana – em várzea e igapó. As emissões foram relacionadas à química da água intersticial, ao potencial de produção de metano (MPP) e à biomassa radicular.As emissões foram maiores na várzea, independentemente da espécie ou da altura no tronco. A várzea apresentou maior condutividade, maiores concentrações de CH4 dissolvido e maior MPP, pH próximo à neutralidade e menor oxigênio, com raízes finas concentradas nos primeiros 50 cm do solo. Emissões basais correlacionaram‐se com a química superficial e a biomassa radicular na várzea, mas não no igapó.Os resultados indicam que as emissões são controladas principalmente pela biogeoquímica superficial do sítio, devendo ser incorporadas a modelos de CH4 em escala de bacia. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
Description
Abstract:Summary: Tree stems in Amazonian floodplains emit substantial methane (CH4), yet controls on emission variability remain unclear. Emissions span orders of magnitude between várzea (nutrient‐rich) and igapó (nutrient‐poor) forests and among trees, suggesting controls beyond flooding.We tested whether site‐level biogeochemistry better explains stem CH4 variability than species identity by measuring emissions from two co‐occurring species with contrasting wood densities – Eschweilera coriacea and Hevea spruceana – across várzea and igapó forests. Emissions were paired with porewater chemistry (electrical conductivity, dissolved oxygen, dissolved CH4, and dissolved organic carbon), methane production potential (MPP), and root biomass.Stem CH4 emissions were significantly higher in várzea than in igapó, independent of species or stem height. Várzea porewaters displayed higher conductivity, dissolved CH4 and MPP, near‐neutral pH, and lower oxygen, with fine roots concentrated in the 0‐ to 50‐cm soil layer, indicating a shallow CH4 supply zone. Basal stem emissions in várzea correlated with shallow porewater chemistry and fine‐root biomass, whereas relationships in igapó were weak.These findings show that Amazonian floodplain stem CH4 emissions are governed by shallow site‐level biogeochemistry, rather than species identity alone and should be incorporated into basin‐scale CH4 budgets and process models to capture spatial variability. [ABSTRACT FROM AUTHOR]
ISSN:0028646X
DOI:10.1111/nph.71168