Pathways of N2O production and associated isotope effects in arable and grassland soils with special emphasis on the distinction between fungal and bacterial denitrification
The aim of this research is a better understanding of the pathways of N2O emissions from soil. Isotope analysis and inhibition experiments are used to discriminate between N2O produced during denitrification from bacteria or fungi.
The greenhouse gas N2O is formed by various microbiological processes in soils, where nitrification and denitrification play the major role. The contribution to N2O formation of each microbial community is not sufficiently explored yet. Denitrification is conducted by both bacteria and fungi, but currently, N2O formation by fungal denitrification is probably underestimated. A better understanding of sources of N2O is essential for developing mitigation measures to reduce N2O emissions.
The project is a collaboration between the University of Göttingen - Institute of Grassland Science, the Thünen Institute for Climate Smart Agriculture and the Technion - Israel Institute of Technology, Haifa. It aims at developing a new integrative method, based on FTIR spectroscopy for continuous monitoring of isotopic nitrogen species in soils as a tool to investigate short-term isotope and isotopologue dynamics and N2O formation.
The aim of our project part is to quantify the contribution of fungi and bacteria on N2O formation in soils as well as the associated isotope effects. We conduct incubation experiments to gain information on N2O formation from denitrification and to show simultaneously the fungal and bacterial contributions to N2O formation. Isotope effects of the source processes of N2O emissions will be determined to check, how isotopic signatures can be used to identify these processes.
Science, Federal Ministry of Food and Agriculture, associations of agriculture and environmental protection
Laboratory experiments are conducted with pure cultures and soils:
Incubation experiments with six soil fungi were used to characterize N2O produced during fungal denitrification, with special emphasis on 15N site preference (SP) of N2O to check how SP of N2O is different from bacterial denitrification. The existence of oxygen exchange between water and denitrification intermediates during fungal denitrification was checked in a tracer experiment using 18O-enriched water.
Incubation experiments were conducted with arable and grassland soils to distinguish between N2O produced during bacterial and fungal denitrification using microbial growth inhibitors.
Pure culture experiments:
Is N2O from six fungi characterized by higher SP-values compared to N2O from bacteria?
Do fungi have an oxygen exchange between water and dentrification intermediates?
Do microbial growth inhibitors serve to differentiate between N2O produced during denitrification by bacteria and fungi?
Do fungi existing in a soil community produce N2O isotope values comparable to values known from pure fungal cultures?
Rohe, L., Anderson, T.-H., Braker, G., Flessa, H., Giesemann, A., Wrage-Mönnig, N. and Well, R. (2014). Fungal oxygen exchange between denitrification intermediates and water. Rapid Commun. Mass Spectrom., 28: 377–384. doi:10.1002/rcm.6790
Rohe, L., Anderson, T.-H., Braker, G., Flessa, H., Giesemann, A., Lewicka-Szczebak, D., Wrage-Mönnig, N. and Well, R. (2014).Dual isotope and isotopomer signatures of nitrous oxide from fungal denitrification – a pure culture study. Rapid Commun. Mass Spectrom., 28, 1893–1903. doiI: 10.1002/rcm.6975
4.2010 - 6.2013
Project status: finished