Nitrous oxide (N2O) is a potent greenhouse gas mainly emitted from agriculture. In the biological process of denitrification, intermediates of the nitrogen cycle are reduced under oxygen limiting conditions thereby releasing N2O. Denitrification is influenced by various environmental factors and both bacteria and fungi are capable of denitrification. The ultimate aim of this thesis was to determine the significance of fungal and bacterial denitrification in arable soil and to investigate influences of soil pH and physical disturbance on potential denitrification rates and denitrifying communities. Long-term pH plots combined with a disturbance gradient have been utilised to investigate fungal and bacterial denitrification distinguished by application of selective inhibitors. Highest N2O production was measured from slightly acidic soil and soil with reduced disturbance. Fungi and bacteria contributed to N2O production with bacterial denitrification as dominant source. Fungal denitrification remained unaffected by soil pH and disturbance whereas bacterial denitrification was influenced by these factors. Bacterial denitrification was positively correlated with concentrations of fatty acids which suggested that these fatty acids were common to bacteria involved in N2O production in the soils investigated here. Bacterial community structure changed with soil pH and disturbance whereas fungal community structure was only influenced by disturbance. Bacterial denitrifier communities (nitrite reductases nirK and nirS) changed over the pH gradient but only the nirK community was affected by disturbance. This indicated that groups of bacterial denitrifiers follow different ecological strategies. Gene abundance of nirK and nirS was also correlated to concentrations of the fatty acids associated with denitrifying bacteria in the soils investigated here. In conclusion, fungal denitrification was significant in arable soil but remained unchanged by soil pH and disturbance. Therefore, fungal denitrification is important in agricultural ecosystems and should be considered when developing mitigation strategies for N2O production especially under conditions favourable for fungal denitrification.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:553807 |
| Date | January 2011 |
| Creators | Herold, Miriam B. |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=179366 |
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