Greenhouse gas fluxes over Central European grasslands

Wednesday, 17 December 2014: 11:35 AM
Lukas Johannes Hörtnagl1, Michael Bahn2, Matthias Barthel1, Werner Eugster1, Katja Klumpp3, Thomas Ladreiter-Knauss2, Lutz Merbold1, Georg Wohlfahrt2 and Nina C Buchmann1, (1)ETH Swiss Federal Institute of Technology Zurich, Zurich, Switzerland, (2)University of Innsbruck, Institute of Ecology, Innsbruck, Austria, (3)INRA, Grassland Ecosystem Research, Clermont-Ferrand, France
The uptake of carbon dioxide (CO2) by grassland ecosystems can be offset by the concurrent emission of the greenhouse gases methane (CH4) and nitrous oxide (N2O) in terms of CO2-equivalents. As a consequence, CH4 and N2O emissions can contribute to an increase of the global warming potential (GWP) of the respective study site. For a full assessment of the climatic impact of grassland ecosystems it is therefore necessary to quantify fluxes of these two compounds in combination with CO2 exchange. Since agricultural management practices and land use change at a given site can have a strong impact on annual CH4 and N2O budgets, both compounds are a frequent topic of discussion when planning GHG mitigation strategies.Here we present an overview of the GHG exchange of eight managed Central European grassland sites along a gradient of elevation and land use intensity. Fluxes of the three major GHGs CO2, CH4 and N2O were quantified using the eddy covariance or chamber technique. The grasslands differed with regard to the amount of fertilizer input, frequency of cuts and grazing duration and intensity, ranging from more intensively managed to very lightly managed and abandoned grassland.

In this presentation we focus on time periods when measurements of all three compounds were available for all sites. We investigate common features among observed CH4 and N2O exchange patterns at the different grassland sites in relation to management activities and concurrently measured biotic / abiotic parameters. In addition, we evaluate the impact of CH4 and N2O fluxes on the annual GWP of field sites for which long-term measurements are available.