Effect of Microbial Activity and Nitrogen Mineralization on Free-living Nitrogen Fixation in Permanent Grassland Soils |
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| Authors: | A K Patra X Le Roux L Abbadie A Clays-Josserand F Poly P Loiseau F Louault |
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| Institution: | Authors' addresses: Dr A. K. Patra (corresponding author;e-mail: or ), Dr X. Le Roux, Dr A. Clays-Josserand and Dr F. Poly, UMR 5557 Ecologie Microbienne (CNRS-UniversitéLyon 1, USC 1193 INRA), IFR41, 43 boulevard du 11 novembre 1918, 69622 Villeurbanne, France;Dr L. Abbadie, UMR 7625 Ecologie (CNRS-UniversitéParis 6-ENS), 45 rue d'Ulm, 75005 Paris, France;Dr P. Loiseau and Dr F. Louault, Unitéd'Agronomie (INRA), site de Crouel, 234 avenue du Brézet, 63039 Clermont Ferrand, France |
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| Abstract: | Free‐living nitrogen (N) fixation can be important for sustainable soil fertility, particularly in extensively managed soils with low abundance of leguminous plant species. However, the factors affecting free N2‐fixation in situ are still poorly documented. We investigated the role of microbial active biomass activity, particularly substrate‐induced respiration (SIR) and net N mineralization, on the free‐living N2 fixation in soils under a semi‐natural grassland ecosystem in France. Analysis of replicated bulk soil and rhizospheric soil samples obtained from sites experiencing contrasting grazing regimes revealed highly significant negative relationships (P < 0.01) between free‐living N2‐fixation and SIR or N‐mineralization with a significant rhizosphere effect. The study has demonstrated that the activity of free‐living N2‐fixers is more important in soils having low active microbial biomass and low N‐mineralization rates in these permanent grasslands. |
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| Keywords: | carbon mineralization free-living N2-fixation grasslands microbial activity N-cycling N-mineralization |
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