Atmospheric CO2 elevation has little effect on nitrifying and denitrifying enzyme activity in four European grasslands |
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| Authors: | Romain Barnard Laure Barthes Xavier Le Roux† Harry Harmens‡ Antonio Raschi§ Jean-FranÇois Soussana¶ Barbro Winkler&#; Paul W Leadley |
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| Institution: | UniversitéParis-Sud XI, Laboratoire d'Ecologie, Systématique et Evolution, UMR CNRS 8079, F-91405 Orsay Cedex, France,;Ecologie Microbienne, UMR 5557 (CNRS –UniversitéLyon 1 –USC 1196 INRA), 43 Bd du 11 Novembre 1918, F-69622 Villeurbanne Cedex, France,;Centre for Ecology and Hydrology Bangor, University of Wales Bangor, Deiniol Road, Bangor, Gwynedd LL57 2UP, UK,;CNR–IATA, Piazzale delle Cascine 18, 50144 Firenze, Italy,;INRA, Unitéd'Agronomie, Equipe FGEP, 234 Av. Brezet, F-63100 Clermont-Ferrand, France,;GSF National Research Center, Institute of Soil Ecology, Department of Environmental Engineering, Ingolstaedter Landstr. 1, D-85759 Oberschleissheim, Germany |
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| Abstract: | The objective of this study was to determine what patterns, if any, existed in the response of nitrifying enzyme activity (NEA), denitrifying enzyme activity (DEA), soil microbial N and soil inorganic N to elevated CO2 across a broad range of grassland environments. We studied the response of these N pools and microbial activities in four CO2‐enrichment sites of the MEGARICH project (Managing European Grasslands as a Sustainable Resource in a Changing Climate). CO2 treatment was studied in factorial combination with a cutting frequency treatment at two sites and with a temperature treatment at one site. Our study showed that microbial biomass N, NEA, DEA and extractable soil NH4+] and NO3?] were generally not affected by elevated CO2 in these grassland ecosystems after several years of treatment, nor by cutting frequency or temperature at the sites that included these treatments. Exceptions to this were that DEA and soil NO3?] decreased by 22% and 45%, respectively, at the French site at elevated CO2. We discuss the possible explanations for this lack of response. |
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| Keywords: | ammonium global change immobilization MEGARICH project nitrate |
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