Abstract: Aims and Methods Vascular plants are known to influence the production, transport and oxidation of methane in wetland soils, but these processes are not well understood. Using plants grown in intact peat cores, we compared the influence upon methane emissions of 20 forb and graminoid species from European wetlands. We measured plant-mediated transport of methane (conduit or chimney effect) using a novel agar-sealing technique that prevented methane exchange from the bare soil to the atmosphere.Important Findings The plant-mediated transport (chimney effect) represented between 30% and almost 100% of the total methane flux, with graminoids exhibiting greater internal transport than forbs. In general, plants with less dense root tissues and a relatively larger root volume exhibited a larger chimney effect. Most species (12 out of 20) significantly reduced methane emissions compared to bare soil and only one species, Succisa pratensis, increased them. We suggest that characterising vegetation in terms of plant functional traits and plant processes offers an effective method for estimating methane emissions from wetlands. However, we found no correlation between the magnitude of the chimney effect and the overall influence of different plant species on methane emissions. Besides introducing a useful tool to study plant-mediated transport, this work suggests that characterising vegetation in terms of functional traits could improve estimates of methane emissions from wetlands, which in turn could help in designing mitigation strategies.

Key words: functional group, graminoid, forb, agar-sealing, conduit, gas transport