Work

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

Year: 2026

Type: article

Abstract: Summary Tree stems in Amazonian floodplains emit substantial methane (CH 4 ), 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 CH 4 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 CH 4 , and dissolved organic carbon), methane production potential (MPP), and root biomass. Stem CH 4 emissions were significantly higher in várzea than in igapó, independent of species or stem height. Várzea porewaters displayed higher conductivity, dissolved CH 4 and MPP, near‐neutral pH, and lower oxygen, with fine roots concentrated in the 0‐ to 50‐cm soil layer, indicating a shallow CH 4 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 CH 4 emissions are governed by shallow site‐level biogeochemistry, rather than species identity alone and should be incorporated into basin‐scale CH 4 budgets and process models to capture spatial variability.

Source: New Phytologist

DOI: 10.1111/nph.71168