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| Titel |
The partitioning of N2O emissions between denitrification and other sources in natural and semi-natural land use types in the UK. |
| VerfasserIn |
Fotis Sgouridis, Sami Ullah |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250145276
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| Publikation (Nr.) |
 EGU/EGU2017-9199.pdf |
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| Zusammenfassung |
| Natural and semi-natural terrestrial ecosystems (unmanaged peatlands and forests, extensive
and intensive grasslands) have been under-represented in the UK greenhouse gas
(GHG) inventory, thus increasing the uncertainty of annual GHG emission estimates.
This uncertainty is further exacerbated by the high spatio-temporal variability of
the processes responsible for nitrous oxide (N2O) emission. The partitioning of
N2O emission to its different sources can further improve our understanding of the
controls on the different microbial processes responsible for N2O production and
consumption and ultimately inform GHG mitigation strategies. We have measured in
situ N2O fluxes from natural and semi-natural ecosystems in two replicated UK
catchments monthly between April 2013 and October 2014. An adapted 15N-Gas Flux
method1 for low level additions of 15N tracer (0.03 - 0.5 kg 15N ha−1) appropriate for
natural (unfertilised) ecosystems was used to quantify denitrification2 and elucidate
its relative contribution to net N2O production. Total N2O fluxes were 40 times
higher in the intensive grasslands than in the peatlands and ranged between 0.05 and
1.98 kg N ha−1 y−1. The mean contribution of denitrification to the total N2O flux
(DN2O/TN2O) ranged between 9 and 59 % and was lowest in a well-drained forest and
highest in a poorly-drained forest soil, while in peatlands and grassland soils it
was 48% and 41% on average, respectively. Soil moisture was shown as the key
environmental driver regulating the partitioning of N2O between denitrification and
other sources (r2=0.46) across land use types. Total N2O fluxes across land use
types were explained by a simple regression model (r2=0.83) including parameters
such as total dissolved nitrogen, organic carbon availability and volumetric water
content. Nitrous oxide emission factors (EFs) calculated as a fraction of mineral N
inputs averaged at 0.4 and 0.9% for the semi-improved and improved grasslands,
respectively. Using simulated atmospheric N-deposition data we have estimated
the fraction of N deposition-induced N2O emissions from poorly drained forest,
well drained forest and organic soils to be 0.5, 1.6 and 0.3%, respectively. The
assumption that 1% of the deposited N on natural ecosystems is emitted as N2O,
may over or under-estimate this source and further information on N2O sources
as well as the development of Tier 2 emission factors should help constrain this
uncertainty.
References
1Sgouridis F, Stott A & Ullah S, 2016. Application of the 15N-Gas Flux method for
measuring in situ N2 and N2O fluxes due to denitrification in natural and semi-natural terrestrial
ecosystems and comparison with the acetylene inhibition technique. Biogeosciences, 13,
1821-1835.
2Sgouridis F & Ullah S, 2015. Relative magnitude and controls of in situ N2 and
N2O fluxes due to denitrification in natural and semi-natural terrestrial ecosystems
using 15N tracers. Environmental Science & Technology, vol. 49(24), 14110-14119. |
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