Nitrogen addition differently alters GHGs production and soil microbial community of tidal salt marsh soil depending on the types of halophyte

Temperate tidal salt marshes are an important carbon sink. They store 44.7 Tg C and only emit low amounts of greenhouse gases. Although recent studies have suggested that environmental changes such as eutrophication and plant invasion may alter their methane and nitrous oxide emissions, the exact consequences and dynamics are not yet fully understood. We hypothesize that the greenhouse gas emission responses from nitrogen addition differs depending on halophyte types. In this study, we conducted soil incubation experiments with different halophyte and nitrogen amendments. We found that nitrogen addition significantly enhanced methane emissions from bare tidal flats (45%) and Suaeda japonica marshes (3500%), which normally have low plant biomass nitrogen input. The main contributors to this change were the increased abundance of Gram-positive bacteria and decreased relative abundance of sulfate to methanogen reducers (dsrA/mcrA). These results suggest that the effects of nitrogen addition on methane emission stimulation may be substantial for specific types of tidal marshes. They further suggests that improper nitrogen input management and the consequent eutrophication may cause a dramatic rise in methane emissions.