Carbon (C) as a driver of soil denitrification was investigated in a series of four laboratory incubation experiments employing stable nitrogen (N) and C isotope approaches. The research addressed the lack of knowledge on mechanisms through which the quantity and quality of organic‐C containing substrates interact with denitrification. The amount of organic matter added to soil was manipulated to relate C respiration with process rates of denitrification. Respiration derived from dissolved organic matter C was linearly related to denitrification but the direction of the relationship was variable in time. This may be most likely an effect of changing quality of the C available and possibly microbial community structure. Nitrous oxide (N2O) emission from denitrification at the later stages of residue decomposition was driven by nitrate (NO3‐) accumulation in the soil rather than C provided by the residue. Denitrification across a vertical shallow soil profile formed in a laboratory microcosm was investigated. A surface hotspot formed immediately as a response to residue‐C addition and increased rates of N2O production. N2O reduction occurred at depth. The hotspot at depth was related to an indirect effect of residue‐C, which was depletion of O2. Further, to address the complexity of low molecular weight C substrate available to denitrifiers in the soil solution, denitrification rates in response to glucose, citric acid and glutamic acid supplied individually versus in mixture were characterised. Carbon substrate quality regulated N2O production rates via interactions within the soil microbial community and with the soil solid phase. Overall, the experiments showed that C stimulates strong N2O emission peaks and increase cumulative N2O emissions from arable soil along a gradient of varying C substrate complexity and quantity. Interaction in space and time play an important role when C containing inputs affected other proximal drivers of denitrification such as NO3‐ and O2.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:715494 |
| Date | January 2017 |
| Creators | Kuntz, Marianne |
| 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=232081 |
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