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There are three major pathways by which gases produced in wetland soils can be emitted to the atmosphere: diffusion, transport through plants, and ebullition. The rate of diffusion of gases out of a wetland soil is a function of the concentration gradient between soil pore spaces and the overlying water column or atmosphere, the wetness of the soil, and the amount of atmospheric/water column turbulence (Lai, 2009; Le Mer & Roger, 2001). Because molecular diffusion is a relatively slow process, rates of CH₄ oxidation can be more important when diffusion is the major route of export from the wetland (Bridgham et al., 2013). However, while a low water table increases the distance CH₄ has to diffuse through oxidized soils and therefore provides more opportunities for the aerobic oxidation of CH₄ (Roslev & King, 1996), this can occur at the radiative expense of higher rates of N₂O production (Pärn et al., 2018).

The aerenchyma tissues that allow vascular wetland plants to transport O₂ to their roots permit gases produced in soils to be efficiently vented through plants by passive diffusion or (faster) convective gas flows (Colmer, 2003). Gas transport through both herbaceous and woody plants can account for a substantial portion of total wetland CH₄ emissions (Covey & Megonigal, 2019; Gauci et al., 2010; Neubauer et al., 2000; Pangala et al., 2017; Whiting & Chanton, 1992). Methane that is transported through plants spends less time in oxidized surface soils and therefore is less susceptible to being oxidized to CO₂ (Joabsson et al., 1999), although CH₄ oxidation can be enhanced in the rhizosphere due to root O₂ loss (van Bodegom et al., 2001). There is a temporal coupling between CH₄ production and emission in vegetated wetlands, but this relationship breaks down in unvegetated sediments because the lack of vegetation reduces CH₄ emissions and promotes transient CH₄ storage (Reid et al., 2013) that leads to enhanced ebullition.

Ebullition (bubbling) occurs when the local hydrostatic pressure decreases due to changes in temperature, air pressure, and water levels (Chanton et al., 1989; Männistö et al., 2019; Tokida et al., 2007), allowing gas bubbles to rise. As with plant‐mediated gas transport, the rapid vertical movement of gas bubbles allows CH₄ to quickly transit active CH₄ oxidation regions (Lai, 2009). Rates of ebullition are spatially patchy and temporally variable but can be the major route of CH₄ transport from some wetlands (Devol et al., 1988; Goodrich et al., 2011; Walter et al., 2006). The importance of ebullition can be substantially lower for CO₂ and N₂O due to their higher solubility (McNicol et al., 2017). Because gas transport through plants helps prevent the accumulation of gases in soil pore spaces (Reid et al., 2013), ebullition is likely to be most important in unvegetated wetlands or those with few vascular plants (Stanley et al., 2019).