Interspecific and spatial differences in nitrogen uptake in monocultures and two-species mixtures in north European grasslands

Authors

  • A. Jumpponen,

    Corresponding author
    1. Section of Soil Science, Department of Forest Ecology, Swedish University of Agricultural Sciences, S-90183 Umeå, Sweden, and
    2. Section of Crop Science, Department of Agricultural Research for Northern Sweden, Swedish University of Agricultural Sciences, S-90403 Umeå, Sweden
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    • Present address: Division of Biology, 125 Ackert Hall, Kansas State University, Manhattan, KS 66506, USA.

  • P. Högberg,

    1. Section of Soil Science, Department of Forest Ecology, Swedish University of Agricultural Sciences, S-90183 Umeå, Sweden, and
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  • K. Huss-Danell,

    1. Section of Crop Science, Department of Agricultural Research for Northern Sweden, Swedish University of Agricultural Sciences, S-90403 Umeå, Sweden
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  • C. P. H. Mulder

    1. Section of Soil Science, Department of Forest Ecology, Swedish University of Agricultural Sciences, S-90183 Umeå, Sweden, and
    2. Section of Crop Science, Department of Agricultural Research for Northern Sweden, Swedish University of Agricultural Sciences, S-90403 Umeå, Sweden
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    • Present address: Institute of Arctic Biology, University of Alaska, Fairbanks, AK 99775, USA.


§Author to whom correspondence should be addressed. E-mail: ari@ksu.edu

Summary

1. To study the potential for complementarity in nitrogen acquisition from different soil depths, we injected an isotope tracer (15NH4Cl) at 5 and 20 cm depths in plant communities containing Achillea millefolium L. and Festuca ovina L. or Phleum pratense L. and Trifolium pratense L. in monocultures and two-species mixtures.

2. In monoculture, Festuca and Phleum took up tracer at 5 and 20 cm depths. In contrast, Achillea and Trifolium monocultures acquired the tracer mainly from 5 cm depth. In two-species mixtures, all four species took up tracer at 5 cm depth.

3.Achillea N acquisition from 20 cm depth increased in mixture with Festuca in comparison to that in monoculture; Festuca N acquisition from 20 cm depth decreased, although not significantly. Trifolium N acquisition remained unchanged when grown in mixture with Phleum. Phleum behaved like Festuca: its N acquisition from 20 cm depth in mixture was reduced in comparison to monoculture.

4. Our data on Festuca and Achillea support spatial partitioning in resource acquisition. This was not evident in Phleum and Trifolium mixture, potentially because Trifolium relied on N2 fixation as N source.

5. These results demonstrate spatial variation among plant species and plant communities in their N acquisition in the field.

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