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Research article - Peer-reviewed, 2014

Does nitrogen transfer between plants confound N-15-based quantifications of N-2 fixation?

Carlsson, Georg; Huss-Danell, Kerstin; Carlsson, Georg


Transfer of fixed N from legumes to non-legume reference plants may alter the N-15 signature of the reference plant as compared to the soil N available to the legume. This study investigates how N transfer influences the result of N-15-based N-2 fixation measurements.We labelled either legumes or non-legumes with N-15 and performed detailed analyses of N-15 enrichment in mixed plant communities in the field. The results were used in a conceptual model comparing how different N transfer scenarios influenced the N-15 signatures of legumes and reference plants, and how the resulting N-2 fixation estimate was influenced by using reference plants in pure stand or in mixture with the legume.Based on isotopic signatures, N transfer was detected in all directions: from legume to legume, from legume to non-legume, from non-legume to legume, from non-legume to non-legume. In the scenario of multidirectional N transfer, N-2 fixation was overestimated by using a reference plant in pure stand.Fixed N transferred to neighbouring reference plants modifies the N-15 signature of the soil N available both to the reference plant and the N-2-fixing legume. This provides strong support for using reference plants growing in mixture with the legumes for reliable quantifications of N-2 fixation.


Legumes; N-2 fixation; Reference plant; N-15 natural abundance; N-15 isotope dilution

Published in

Plant and Soil
2014, Volume: 374, number: 1-2, pages: 345-358
Publisher: Springer Verlag (Germany)

    SLU Authors

      • Huss-Danell, Kerstin

        • Department of Agricultural Research for Northern Sweden, Swedish University of Agricultural Sciences

      UKÄ Subject classification

      Other Agricultural Sciences not elsewhere specified

      Publication Identifiers


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