Reduced N cycling in response to drought, warming, and elevated CO2 in a Danish heathland: Synthesizing results of the CLIMAITE project after two years of treatments

• Published in: Global Change Biology
• Language: English
• Published: Wiley-Blackwell 2011
• Subjects: Life Sciences; Christensen; Andreas; Sven; Klaus; Mikkelsen; Michelsen; Andresen; Iks; Arndal; National Environmental Research Institute
• Online Access: http://hdl.handle.net/2262/56640; https://doi.org/10.1111/j.1365-2486.2010.02351.x

Abstract Field-scale experiments simulating realistic future climate scenarios are important tools for investigating the effects of current and future climate changes on ecosystem functioning and biogeochemical cycling. We exposed a semi-natural Danish heathland ecosystem to elevated atmospheric carbon dioxide (CO2), warming, and extended summer drought in all combinations. Here, we report on the short-term responses of the nitrogen (N) cycle after two years of treatments. Elevated CO2 significantly affected above-ground stoichiometry by increasing the carbon to nitrogen (C/N) ratios in the leaves of both co-dominant species (Calluna vulgaris and Deschampsia flexuosa), as well as the C/N ratios of Calluna flowers and by reducing the N concentration of Deschampsia litter. Below-ground, elevated CO2 had only minor effects, whereas warming increased N turnover, as indicated by increased rates of microbial NH4+-N consumption, gross mineralization, potential nitrification, denitrification and N2O emissions. Drought reduced below-ground gross N mineralization and decreased fauna N mass and N mineralization. Leaching was unaffected by treatments but was significantly higher across all treatments in the second year than in the much drier first year indicating that ecosystem N loss is highly sensitive to changes and variability in amount and timing of precipitation. Interactions between treatments were common and although some synergistic effects were observed, antagonism dominated the interactive responses in treatment combinations, i.e. responses were smaller in combinations than in single treatments. Nonetheless, increased C/N ratios of photosynthetic tissue, decreased litter N production, and decreased fauna N mineralization prevailed in the full treatment combination indicating reduced N turnover in the simulated future climate scenario, which could act to reduce the potential growth response of plants to elevated atmospheric CO2 concentration. In conclusion, effects observed in single-factor studies should be evaluated with caution. Multi-factor climate experiments are needed for improving realistic estimation of the combined ecosystem responses to future climate changes. : Michelsen, Anders, [e-mail] merged with this user on 26-Jan-2010 by Shekar, Rachel (Michelsen, Anders) [e-mail] (Larsen, Klaus Steenberg) [e-mail] (Andresen, Louise C.) [e-mail] (Beier, Claus) [e-mail] (Jonasson, Sven) [e-mail] (Albert, Kristian R.) [e-mail] (Ambus, Per) [e-mail] (Stevnbak, Karen) [e-mail] (Arndal, Marie Frost) [e-mail] (Carter, Mette S.) [e-mail] (Christensen, Soren) [e-mail] (Holmstrup, Martin) [e-mail] (Ibrom, Andreas) [e-mail] (Kongstad, Jane) [e-mail] (van der Linden, Leon) [e-mail] (Maraldo, Kristine) [e-mail] (Michelsen, Anders) [e-mail] (Mikkelsen, Teis N?rgaard) [e-mail] (Pilegaard, Kim) [e-mail] (Prieme, Ambers) [e-mail] (Ro-Poulsen, Helge) [e-mail] (Schmidt, Inger K. Kappel) [e-mail] (Selsted, Merete Bang) Technical University of Denmark, Ris? National Laboratory for Sustainable Energy, Biosystems Division - Roskilde - DENMARK (Larsen, Klaus Steenberg) University of Copenhagen, Institute of Biology - Copenhagen - DENMARK (Andresen, Louise C.) Technical University of Denmark - Roskilde - DENMARK (Beier, Claus) Technical University of Denmark, Ris? National Laboratory for Sustainable Energy, Biosystems Division - Roskilde - DENMARK (Beier, Claus) University of Copenhagen, Institute of Biology - Copenhagen - DENMARK (Jonasson, Sven) Ris? National Laboratory for Sustainable Energy, Technical University of Denmark, Biosystems Division - Roskilde - DENMARK (Albert, Kristian R.) Technical University of Denmark, Ris? National Laboratory for Sustainable Energy, Biosystems Division - Roskilde - DENMARK (Albert, Kristian R.) Ris? DTU, Biosystems - Frederiksborgvej 399--> - 4000 - Roskilde - DENMARK (Ambus, Per) Technical University of Denmark, Ris? National Laboratory for Sustainable Energy, Biosystems Division - Roskilde - DENMARK (Ambus, Per) University of Copenhagen, Biology - ?. Farimagsgade 2D--> - DK-1353 - Copenhagen - DENMARK (Stevnbak, Karen) University of Copenhagen, Institute of Biology - Copenhagen - DENMARK (Stevnbak, Karen) University of Copenhagen, Forest and Landscape - H?rsholm - DENMARK (Arndal, Marie Frost) Ris? National Laboratory for Sustainable Energy, Technical University of Denmark, Biosystems Division - Frederiksborgvej 399--> , PO box 49--> - 4000 - Roskilde - DENMARK (Carter, Mette S.) Technical University of Denmark, Ris? National Laboratory for Sustainable Energy, Biosystems Division - Roskilde - DENMARK (Carter, Mette S.) DENMARK (Christensen, Soren) University of Copenhagen, Institute of Biology - Copenhagen - DENMARK (Christensen, Soren) National Environmental Research Institute, Terrestrial Ecology - Aarhus - DENMARK (Holmstrup, Martin) Technical University of Denmark, Ris? National Laboratory for Sustainable Energy, Biosystems Department - fredriksborgvej 399--> - 4000 - Roskilde - DENMARK (Ibrom, Andreas) Technical University of Denmark, Ris? National Laboratory for Sustainable Energy, Biosystems Division - Roskilde - DENMARK (Ibrom, Andreas) Ris? Nationa Laboratory for Sustainable Energy, Biosystems Division - (Ibrom, Andreas) University of Copenhagen, Forest and Landscape Ecology - Hoersholm Kongevej 11--> , Dk-2970 Hoersholm--> - Dk-2970 - Hoersholm - DENMARK (Kongstad, Jane) University of Copenhagen, Forest and Landscape - H?rsholm - DENMARK (Kongstad, Jane) RIS?-DTU National Laboratory for Sustainable Energy, Biosystems Division - Building 309--> , PO Box 49--> - 4000 - Roskilde - DENMARK (van der Linden, Leon) Technical University of Denmark, Ris? National Laboratory for Sustainable Energy, Biosystems Division - Roskilde - DENMARK (van der Linden, Leon) National Environmental Research Institute, Department of Terrestrial Ecology - Vejls?vej 25--> - 8600 - Silkeborg - DENMARK (Maraldo, Kristine) National Environmental Research Institute, Terrestrial Ecology - Aarhus - DENMARK (Maraldo, Kristine) Biology, Terrestrial Ecology - Copenhagen - DENMARK (Michelsen, Anders) University of Copenhagen, Institute of Biology - Copenhagen - DENMARK (Michelsen, Anders) Roskilde - DENMARK (Mikkelsen, Teis N?rgaard) Technical University of Denmark, Ris? National Laboratory for Sustainable Energy, Biosystems Division - Roskilde - DENMARK (Mikkelsen, Teis N?rgaard) Technical University of Denmark, Ris? National Laboratory for Sustainable Energy, Biosystems Division - Roskilde - DENMARK (Pilegaard, Kim) Ris? National Laboratory for Sustainable Energy, Technical University of Denmark, Biosystems Division - Roskilde - DENMARK (Pilegaard, Kim) Copenhagen University, Dep. of Biology - S?lvgade 83H--> - 1307 - Copenhagen K - DENMARK (Prieme, Ambers) University of Copenhagen, Institute of Biology - Copenhagen - DENMARK (Prieme, Ambers) University of Copenhagen, Institute of Biology - Copenhagen - DENMARK (Ro-Poulsen, Helge) University of Copenhagen, Forest & Landscape - H?rsholm Kongevej 11--> - 2970 - H?rsholm - DENMARK (Schmidt, Inger K. Kappel) University of Copenhagen, Forest and Landscape - H?rsholm - DENMARK (Schmidt, Inger K. Kappel) Ris? National Laboratory for Sustainabel Energy, DTU , Biosystems - Frederiksborgvej 399--> - 40000 - Roskilde - DENMARK (Selsted, Merete Bang) Technical University of Denmark, Ris? National Laboratory for Sustainable Energy, Biosystems Division - Roskilde - DENMARK (Selsted, Merete Bang) DENMARK