Nordin A, Gunnarsson U
Amino acid accumulation and growth of Sphagnum under different levels of N deposition
Ecoscience: 2000 7:474-480
Nitrogen (N) is a critical nutrient for Sphagnum mosses dominating mire ecosystems. We simulated N deposition hy adding doses of NH4NO3 (0, 1, 3, 5 and 10 g m(-2) yr(-1)) to two Swedish mires with different levels of background atmospheric N deposition, i.e., on Luttumyren in central Sweden 0.3-0.4 g N m(-2) yr(-1) and 0.7-1.1 g N m(-2) yr(-1) on Akhultmyren in south Sweden. After two years of NH4NO3 additions, free amino acid concentrations of S. fuscum, S, magellanicum and S. rubellum from the two nines were analyzed and length growth of the mosses were measured. N additions increased amino acid concentrations in Sphagnum capitula, whereas II decreased Sphagnum length growth. In general, we found that when Sphagnum amino acid N concentrations exceeded 2.0 mg amino acid N g(-1) dry mass, Sphagnum length growth was reduced. The decreased growth did not explain the variation in amino acid concentrations. Hence, increased Sphagnum N assimilation in N treated plots was most likely the factor causing tissue amino acid concentrations to increase. Significant differences among control plots between the two mires in Sphagnum total amino acid N concentrations did not occur. Total amino acid N concentrations of Sphagnum are thus not sensitive enough to reflect differences in N deposition rates when they are below 1.0 g m(-2) yr(-1).
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