Woody stem methane emission in mature wetland alder trees

摘要

Methane (CH_4) is an important greenhouse gas that is predominantly emitted to the atmosphere from anoxic wetland ecosystems. Understanding the sources and emissions of CH_4 is crucially important for climate change predictions; however, there are significant discrepancies between CH_4 source estimates derived via so-called bottom-up and top-down methods. Here we report CH_4 emission from the stems of mature wetland alder (Alnus glutinosa) trees in the UK, a common tree of northern hemisphere flood-plains and wetlands. The alder stems most likely behave as conduits for soil-produced CH_4 either in the gaseous or aqueous phase, and may, therefore, help to reconcile methodological differences in the way the wetland CH_4 source is estimated.rnAlder tree stems emitted average peak CH_4 fluxes of 101 μg CH_4 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 CH_4 flux from the soil surface. The rinding 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 CH_4 flux.