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Multiple processes contribute to methane emission in a riparian cottonwood forest ecosystem
Author(s) -
Flanagan Lawrence B.,
Nikkel Dylan J.,
Scherloski Lauren M.,
Tkach Rachel E.,
Smits Kristian M.,
Selinger L. Brent,
Rood Stewart B.
Publication year - 2021
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.16977
Subject(s) - methane , environmental science , eddy covariance , riparian zone , ecosystem , biogeochemical cycle , atmospheric methane , soil water , forest ecology , riparian forest , hydrology (agriculture) , environmental chemistry , soil science , ecology , atmospheric sciences , chemistry , geology , habitat , biology , geotechnical engineering
Summary Methane emission from trees may partially or completely offset the methane sink in upland soils, the only process that has been regularly included in methane budgets for forest ecosystems. Our objective was to analyze multiple biogeochemical processes that influence the production, oxidation and transport of methane in a riparian cottonwood ecosystem and its adjacent river. We combined chamber flux measurements on tree stems, forest soil and the river surface with eddy covariance measurements of methane net ecosystem exchange. In addition, we tested whether methanogens were present in cottonwood stems, shallow soil layers and alluvial groundwater. Average midday peak in net methane emission measured by eddy covariance was c . 12 nmol m −2 s −1 . The average uptake of methane by soils (0.87 nmol m −2 s −1 ) was largely offset by tree stem methane emission (0.75 nmol m −2 s −1 ). There was evidence of methanogens in tree stems but not in shallow soil. Growing season (May–September) cumulative net methane emission (17.4 mmol CH 4 m −2 ) included methane produced in cottonwood stems and methane input to the nocturnal boundary layer from the forest and the adjacent river. The multiple processes contributing to methane emission illustrated the linked nature of these adjacent terrestrial and aquatic ecosystems.