Abstract: Abstract Aims Ombrotrophic peatland, dominated by Sphagnum, are important carbon sinks for terrestrial ecosystems. The dynamics of growth and decomposition of dominant plants determine the carbon sink potential of ombrotrophic peatland. However, the effects of nitrogen deposition on the growth and decomposition of mosses in ombrotrophic peatland are still controversial. Moreover, the effects of nitrogen deposition on the growth and decomposition of dominant mosses in subtropical ombrotrophic peatlands are rarely reported. Methods We selected an ombrotrophic peatland in southwestern Hubei Province as the study area. Different concentrations of NH4Cl solution were sprayed in situ, and biomass harvesting method and decomposition bag method were adopted to estimate growth and litter decomposition of Sphagnum palustre and Polytrichum commune. Important findings (1) The effects of nitrogen deposition on the growth height and biomass of the two mosses were "low promoting and high inhibiting", and there was a certain nitrogen deposition load for the growth of the two mosses, which was about 3 g N·m-2·y-1. (2) The effects of nitrogen deposition on the growth of the two mosses were different, and the response sensitivity of Sphagnum palustre to nitrogen deposition was greater than that of Polytrichum commune. (3) High nitrogen deposition (6 gN·m-2·y-1and 12g N·m-2·y-1) inhibited the decomposition of Sphagnum palustre, while the effect of low nitrogen deposition (3 g N·m-2·y-1) on the decomposition of Sphagnum palustre depend on time, and all concentrations of nitrogen deposition inhibited the decomposition of Polytrichum commune litter. (4) After one year of decomposition, the average final mass residual rate of Sphagnum palustre was 91.20%-116.09%, and 71.52%-79.07% for Polytrichum commune. The decomposition rate of Polytrichum commune was much higher than that of Sphagnum palustre. (5) Nitrogen deposition significantly affected the chemical element content and stoichiometric ratio of the two moss litters, and was closely related to decomposition time.

Key words: bog, decomposition, moss, nitrogen input, production