Plant-mediated C[H.sub.4] transport and C gas dynamics quantified in-situ in a Phalaris arundinacea-dominant wetland

Northern peatland methane (C[H.sub.4]) budgets are important for global C[H.sub.4] emissions. This study aims to determine the ecosystem C[H.sub.4] budget and specifically to quantify the importance of Phalaris arundinacea by using different chamber techniques in a temperate wetland. Annually, roughly 70 ± 35% of ecosystem C[H.sub.4] emissions were plant-mediated, but data show no evidence of significant diurnal variations related to convective gas flow regardless of season or plant growth stages. Therefore, despite a high percentage of arenchyma, P arundinacea-mediated C[H.sub.4] transport is interpreted to be predominantly passive. Thus, diurnal variations are less important in contrast to wetland vascular plants facilitating convective gas flow. Despite of plant-dominant C[H.sub.4] transport, net C[H.sub.4] fluxes were low (-0.005-0.016 µmol [m.sup.-2] [s.sup.-1]) and annually less than 1% of the annual C-C[O.sub.2] assimilation. This is considered a result of an effective root zone oxygenation resulting in increased C[H.sub.4] oxidation in the rhizosphere at high water levels. This study shows that although C[H.sub.4], having a global warming potential 25 times greater than C[O.sub.2], is emitted from this P arundinacea wetland, less than 9% of the C sequestered counterbalances the C[H.sub.4] emissions to the atmosphere. It is concluded that P arundinacea-dominant wetlands are an attractive C-sequestration ecosystem. Keywords Plant-mediated C[H.sub.4] flux * Automated closed static chambers * Diurnal variation * Phalaris arundinacea