Nitrogen translocation in Sphagnum mosses: effects of atmospheric nitrogen deposition

Authors

  • Allison R. Aldous

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    1. Current address: Cornell University, Department of Natural Resources, Ithaca, New York 14853, USA; The Nature Conservancy, 821 SE 14th Ave, Portland, Oregon 97214, USA
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Author for correspondence: Allison R. Aldous Tel: +1 503 2300707 ext. 342 Fax: +1 503 2309639 Email: aaldous@tnc.org

Summary

  • • Here, the hypothesis was tested that nitrogen (N) translocation from older to younger parts of Sphagnum decreases as N inputs from atmospheric deposition increase.
  • • Nitrogen translocation in Sphagnum mosses was compared in bogs with contrasting atmospheric N deposition (Adirondack – relatively high N deposition; Maine – relatively low) and by following the movement of a 15NH415NO3 tracer applied to plots of Sphagnum capillifolium over 2 yr.
  • • Annual N translocation ranged from 11% to > 80% in the lower and higher influx sites, respectively. Nitrogen translocation was an important process for the N budget of the Sphagnum mosses, contributing 0.5–11% of the annual N requirements. These results suggest that N translocation is as important as direct N retention from atmospheric deposition for the N budget of the mosses. Contrary to expectations, N translocation was greater in the high (Adirondack) than in the low (Maine) deposition sites.
  • • If N translocation is closely tied to water availability, the relative positions of the water tables in the sites over the course of the experiments might account for differences in N translocation among sites. The lower translocation (Maine) sites had lower water tables in the first year of the experiment and experienced a more severe drought in the second year than did the Adirondack sites.

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