Stable carbon and nitrogen isotopes of the moss Haplocladium microphyllum in an urban and a background area (SW China): The role of environmental conditions and atmospheric nitrogen deposition

The C and N concentrations and stable isotopes in new and old tissues of the moss Haplocladium microphyllum were investigated at Guiyang and Gongga Mountain in SW China, aiming at revealing responses of these parameters to different environmental conditions and N deposition, elucidating the effect of N deposition on C fixation and signal variations during senescence. Atmospheric N deposition could be quantified by N in new tissues, showing a level of 30.18 kg N ha−1 yr−1 at Guiyang and 8.46 kg N ha−1 yr−1 at Mt. Gongga, old tissues presented lower C and N concentrations than new tissues, but there was no significant difference between N of new and old tissues at background area with lower N deposition, and the positive effect of N supply on C fixation was observed only for urban mosses under higher N deposition. More negative δ13C mainly indicated the influences of anthropogenic CO2 sources on urban mosses, and higher δ13C of mosses at background area was also related to higher altitude and lower temperature. More negative δ15N of mosses mainly indicated N deposition at Guiyang was dominated by NHx–N from city wastes and sewage, while δ15N of mosses at Mt. Gongga mainly indicated little anthropogenic N pollution in background area. Besides, no significant isotopic difference was found between new and old tissues in both areas, suggesting no isotopic effect occurred during the senescence of H. microphyllum.