Stems of Phragmites australis are buffering methane and carbon dioxide emissions.

Internal concentrations in the culm nodes of Phragmites australis and fluxes of methane (CH) and carbon dioxide (CO) were recorded in the treatment bed of constructed wetland (CW) with subsurface wastewater horizontal flow. Fluxes of CH and CO from the CW treatment bed were in ranges of 0 to 490 μmol m h and from 0 to 4499 μmol m h for CH and CO, respectively. The highest CH soil fluxes were recorded in the unvegetated coarse gravel inflow zone of the CW treatment bed.