Freshwater marshes are the single largest source of atmospheric methane (CH4). Climate change and anthropogenic nitrogen (N)
deposition can alter the production and oxidation of CH4 respectively and thereby also CH4 exchange. But there was little known
about how N regulate key carbon (C) processes, like CH4 production and oxidation under freshwater marshland conditions. In
this study, field-fertilization and incubation experiments were conducted to investigate the effects of four N-fertilization
treatments (0, 6, 12, 24 g N m-2) using ammonium nitrate (NH4NO3) on CH4 production and oxidation and the potential
mechanisms involved, in the Sanjiang Plain, Northeast China. Both the CH4 production and oxidation of N24 (24 g N m-2)
treatment was significantly higher than control and other N treatments. The ammonium nitrogen (NH4+--N), nitrate nitrogen
(NO3---N), dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) concentrations were higher at the N24
treatment compared with the control. The incubation experiment indicated that N-addition stimulated CH4 production more than
CH4 oxidation resulting in net CH4 emission from N-fertilization treatments.