The interactive effect of Juncus effusus and water table position on mesocosm methanogenesis and methane emissions

Abstract

Aerenchymatous plants can affect methane (CH4) emissions from wetland soils differently, and there is a need to understand specifically under which conditions plants enhance or attenuate CH4 emissions. We used a mesocosm set-up to assess the interactive effect of three water table positions (0 cm, −10 cm and −20 cm) and the presence or absence of Juncus effusus L on in vitro soil methanogenesis and methane emissions. Soil methanogenesis and CH4 emission rates were significantly affected by water table position and vegetation, and the effect of vegetation depended on the water table position. At high water tables (−10 cm and 0 cm) soil methanogenesis and CH4 emissions were high and not significantly affected by vegetation, whereas at the low water table (−20 cm), methanogenesis and CH4 emission rates were lower in unvegetated soils than in soils with J. effusus. Methane emissions from organic wetland soils at low water tables may be enhanced by J. effusus because of increased methanogenesis and because CH4 enters the roots in the deeper anaerobic layers and are transported through the aerenchymatous tissue of the plants to the atmosphere bypassing the methanotrophic upper layers of the soils.