Greenhouse gas fluxes over Central European grasslands

Abstract:

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.