Mathematical modelling of methane transport by Phragmites: the potential for diffusion within the roots and rhizosphere

The release of methane into the atmosphere by Phragmites australis (Cav.) Trin. ex Steud. can be considered as a two-stage process. The first, a mainly diffusive movement through the rhizosphere from the anaerobic source regions of the soil and into and along the roots to the root–rhizome junction. The second, the removal of the gas from the root–rhizome junction to the atmosphere through the rhizome–culm system, a process often dominated by convective (pressurised) gas flow. This article addresses the first of these stages and is presented in isolation because of its perceived commonality to wetland plants in general.