On 31.10.2014, Miriam Hurkuck successfully defended her doctoral thesis on „How peatland is affected by neighboring agriculture: Atmospheric nitrogen deposition and potential effects on net ecosystem carbon dioxide exchange at a semi-natural peatland site in Northwestern Germany“ at ETH Zurich.
The main aim of this thesis was to determine atmospheric nitrogen depositions to peatlands in the German-Dutch border area and to quantify potential effects of nitrogen loads on carbon dioxide biosphere-atmosphere exchange. It could be found that the intensive agricultural land use in the Emsland region leads to increased atmospheric nitrogen depositions of about 25 kg ha-1 yr-1 to the neighboring peatland ecosystems which exceed the ecosystem specific critical load about fivefold. The investigated peat bog was a source of carbon dioxide of on average 60 g C m2 yr-1 throughout the experimental period of three years which was in contradiction to the usual function of natural peatlands to act as carbon dioxide sinks. Although no apparent impacts of nitrogen input on ecosystem carbon dioxide exchange could be observed during the investigated period, it can be assumed that long-term exceedances of critical loads lead to shifts in plant species compositions and a subsequent reduction of the carbon dioxide sink strength. As a result, peatlands in close proximity to intensive agricultural land use can substantially contribute to the global greenhouse gas cycle.
Miriam Hurkuck conducted her thesis in the framework of the project INTERREG-IVa (Determination of nitrogen loads from animal husbandry at a semi-natural peatland site in Northwest Germany – ERNST) and successfully finished it within three-and-half years.