Woody stem methane emission in mature wetland alder trees

Gauci, Vincent; Gowing, David J. G.; Hornibrook, Edward R. C.; Davis, Joanna M. and Dise, Nancy B. (2010). Woody stem methane emission in mature wetland alder trees. Atmospheric Environment, 44(17) pp. 2157–2160.

DOI: https://doi.org/10.1016/j.atmosenv.2010.02.034

Abstract

Methane (CH₄) is an important greenhouse gas that is predominantly emitted to the atmosphere from anoxic wetland ecosystems. Understanding the sources and emissions of CH₄ is crucially important for climate change predictions; however, there are significant discrepancies between CH₄ source estimates derived via so-called bottom-up and top-down methods. Here we report CH₄ emission from the stems of mature wetland alder (Alnus glutinosa) trees in the UK, a common tree of northern hemisphere floodplains and wetlands. The alder stems most likely behave as conduits for soil-produced CH₄ either in the gaseous or aqueous phase, and may, therefore, help to reconcile methodological differences in the way the wetland CH₄ source is estimated. Alder tree stems emitted average peak CH₄ fluxes of 101 μg CH₄ m⁻² h⁻¹ (on a stem area basis) in early October, a rate that is similar to that obtained from mature Japanese ash (Fraxinus mandshurica var. japonica) in Japan and amounting to approximately 20% of the measured CH₄ flux from the soil surface. The finding suggests that trees, which occupy 60% of Earth's wetlands and are normally excluded from the measurement programmes that form the basis for bottom-up estimates of the global wetland source, could be important contributors to overall terrestrial ecosystem CH₄ flux.

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