Relationships between denitrification gene expression,dissimilatory nitrate reduction to ammonium and nitrous oxide and dinitrogen production in montane grassland soils |
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| Institution: | 1. Institute of Meteorology and Climate Research, Atmospheric Environmental Research (IMK-IFU), Karlsruhe Institute of Technology (KIT), Garmisch-Partenkirchen 82467, Germany;2. State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China;3. State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences (IBCAS), Beijing 100093, China;4. German Research Center for Environmental Health (GmbH), Research Unit Environmental Genomics, 85764 Neuherberg, Germany;1. Institute of Botany, Department of Environmental Sciences, University of Basel, Schönbeinstrasse 6, 4056 Basel, Switzerland;2. Meteotest, Fabrikstrasse 14, 3012 Bern, Switzerland;3. Federal Office for the Environment, 3003 Bern, Switzerland;1. CNRS – Université des Antilles et de la Guyane, UMR EcoFoG, Campus Agronomique, 97310 Kourou, Guyane Française, France;2. INRA, UR 272 Science du Sol Centre de Recherches d''Orléans, CS 40001, Ardon, 45075 Orléans Cedex 2, France;3. CETIOM, Établissement Public Local d''Enseignement et de Formation Professionnelle Agricole de la Guyane, Savane Matiti, BP 53, 97355 Macouria, Guyane Française, France;4. CETIOM, 1 avenue Lucien Brétignières, 78850 Thiverval-Grignon, France;5. Montpellier SupAgro, UMR SYSTEM (INRA, CIRAD, SupAgro), Bât. 27, 2 place Viala, 34060 Montpellier Cedex 2, France;6. IRD, UMR 210 Eco&Sols, Bât. 12, 2 place Viala, 34060 Montpellier Cedex 2, France;7. INRA, UMR EcoFoG, Campus agronomique, 97310 Kourou, Guyane Française, France;1. Landcare Research, Palmerston North, New Zealand;2. Landcare Research, Lincoln, New Zealand;3. AgResearch, Hamilton, New Zealand;1. Rothamsted Research, North Wyke, Okehampton, Devon EX20 2SB, UK;2. Technical University of Madrid, Chemistry and Agricultural Analysis, Madrid, Spain;3. School of Geography, Earth and Environmental Sciences, University of Plymouth, Davy Building, Drake Circus, Plymouth, Devon PL4 8AA, UK;4. Agri-Food and Biosciences Institute, Newforge Lane, Belfast BT9 5PX, UK;5. Thünen-Institut für Agrarklimaschutz, Bundesallee 50, 38116 Braunschweig, Germany |
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| Abstract: | The montane grassland soils of Europe store significant amounts of nitrogen (N), and climate change might drive their volatilization due to the stimulation of gaseous nitrous oxide (N2O) and dinitrogen (N2) losses. Hence, a thorough, mechanistic understanding of the processes responsible for N loss and retention such as denitrification and dissimilatory nitrate reduction to ammonium (DNRA) in these soils is urgently needed. Here we aimed to explore the relationships between denitrifier gene abundance and expression with N2 and N2O production and the importance of DNRA versus denitrification in nitrate consumption and N2O production for typical montane grassland soils of Southern Germany. In a laboratory incubation experiment with glucose and nitrate addition, we combined direct measurements of N2O and N2 production with a molecular analysis of the denitrifier communities involved in nitrite, nitric oxide (NO) and N2O reduction and with the quantification of DNRA. The soils originated from a space-for-time climate change experiment, where intact plant-soil mesocosms were exposed for three years either to ambient conditions at a high elevation site (“HE” control treatment) or to predicted climate change conditions (warming, reduced summer precipitation and reduced winter snow cover) by translocation to lower elevation (“LE” climate change treatment).The abundance (DNA) of cnorB genes was significantly reduced in LE soils, whereas the abundance of nosZ genes did not differ between the HE and LE soils. However, the decreased abundance of cnorB genes unexpectedly resulted in slightly increased rather than decreased potential N2O emissions. This effect could be explained by the increased levels of cnorB mRNA and, therefore, the higher physiological activity of the NO reducers in the LE soils. In contrast with the DNA levels, the dynamics of the cnorB mRNA levels followed N2O emission patterns, whereas the nosZ expression was strongly correlated with the N2 emission (R2 = 0.83). The potential rates of DNRA were approximately one-third of the rates of denitrification, and DNRA was not a source for N2O.We conclude that DNRA significantly competes with denitrification in these soils, thus contributing to N conservation. This work demonstrates that the molecular analysis of nosZ gene expression has great potential to contribute to solving the enigmatic problem of understanding N2 loss from soil. |
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| Keywords: | Denitrification DNRA Climate change Montane grassland |
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