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Keywords:

  • ammonium;
  • atmospheric nitrogen deposition;
  • denitrifier;
  • dissolved organic nitrogen;
  • moss;
  • nitrogen preference;
  • soil nitrogen availability;
  • stable nitrogen isotope

Summary

  • Mosses, among all types of terrestrial vegetation, are excellent scavengers of anthropogenic nitrogen (N), but their utilization of dissolved organic N (DON) and their reliance on atmospheric N remain uncharacterized in natural environments, which obscures their roles in N cycles.
  • Natural 15N abundance of N sources (nitrate (inline image), ammonium (inline image) and DON in deposition and soil) for epilithic and terricolous mosses was analyzed at sites with different N depositions at Guiyang, China. Moss inline image assimilation was inhibited substantially by the high supply of inline image and DON. Therefore, contributions of inline image and DON to moss N were partitioned using isotopic mass-balance methods.
  • The N contributions averaged 56% and 46% from atmospheric inline image, and 44% and 17% from atmospheric DON in epilithic and terricolous mosses, respectively. In terricolous mosses, soil inline image and soil DON accounted for 16% and 21% of bulk N, which are higher than current estimations obtained using 15N-labeling methods. Moreover, anthropogenic inline image deposition suppressed utilization of DON and soil N because of the preference of moss for inline image under elevated inline image deposition.
  • These results underscore the dominance of, and preference for, atmospheric inline image in moss N utilization, and highlight the importance of considering DON and soil N sources when estimating moss N sequestration and the impacts of N deposition on mosses.