Methane transport and emissions from soil as affected by water table and vascular plants

Abstract

BackgroundThe important greenhouse gas (GHG) methane is produced naturally in anaerobic wetland soils. By affecting the production, oxidation and transport of methane to the atmosphere, plants have a major influence upon the quantities emitted by wetlands. Different species and functional plant groups have been shown to affect these processes differently, but our knowledge about how these effects are influenced by abiotic factors such as water regime and temperature remains limited. Here we present a mesocosm experiment comparing eight plant species for their effects on internal transport and overall emissions of methane under contrasting hydrological conditions. To quantify how much methane was transported internally through plants (the chimney effect), we blocked diffusion from the soil surface with an agar seal.ResultsWe found that graminoids caused higher methane emissions than forbs, although the emissions from mesocosms with different species were either lower than or comparable to those from control mesocosms with no plant (i.e. bare soil). Species with a relatively greater root volume and a larger biomass exhibited a larger chimney effect, though overall methane emissions were negatively related to plant biomass. Emissions were also reduced by lowering the water table.ConclusionsWe conclude that plant species (and functional groups) vary in the degree to which they transport methane to the atmosphere. However, a plant with a high capacity to transport methane does not necessarily emit more methane, as it may also cause more rhizosphere oxidation of methane. A shift in plant species composition from graminoids to forbs and/or from low to high productive species may lead to reduction of methane emissions.

Importance of vegetation classes in modeling CH4 emissions from boreal and subarctic wetlands in Finland

“…Plants serve as the major control of CH 4 emissions from wetlands (Bhullar et al, 2013;Joabsson and Christensen, 2001;Shannon et al, 1996). The different vegetation species effectively influence CH 4 production, oxidation and emissions.…”

Does <i>Juncus effusus</i> enhance methane emissions from grazed pastures on peat?

“…In wetlands, reports on the importance of aerenchymatous plants for CH 4 emissions differ. Most authors have found that emissions from such vegetation are enhanced (Chanton and Dacey, 1991;Greenup et al, 2000;Koelbener et al, 2010;Noyce et al, 2014;Schimel, 1995), but reduced emissions can also occur (Bhullar et al, 2013;Fritz et al, 2011;Grünfeld and Brix, 1999). However, these studies were conducted in permanently flooded wetlands or mesocosms with a high water table.…”

Groundwater impact on methane emissions from flooded paddy fields

“…18,19,20]. However, the muddy layer in a flooded paddy soil is continuously saturated and the impact on the CH 4 cycle of soil moisture driven by groundwater level is negligible.…”