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| Titel |
In Situ Denitrification and Biological Nitrogen Fixation Under Enhanced Atmospheric Reactive Nitrogen Deposition in UK Peatlands |
| VerfasserIn |
Sami Ullah, Ernesto Saiz Val, Fotis Sgouridis, Matthias Peichl, Mats Nilsson |
| 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 |
250140332
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| Publikation (Nr.) |
 EGU/EGU2017-3706.pdf |
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| Zusammenfassung |
| Dinitrogen (N2) and nitrous oxide (N2O) losses due to denitrification and biological N2
fixation (BNF) are the most uncertain components of the nitrogen (N) cycle in peatlands
under enhanced atmospheric reactive nitrogen (Nr) deposition. This uncertainty hampers our
ability to assess the contribution of denitrification to the removal of biologically fixed and/or
atmospherically deposited Nr in peatlands. This uncertainty emanates from the difficulty in
measuring in situ soil N2 and N2O production and consumption in peatlands. In situ
denitrification and its contribution to total N2O flux was measured monthly between April
2013 and October 2014 in peatlands in two UK catchments. An adapted 15N-Gas
Flux method1 with low level addition of 15N tracer (0.03 ± 0.005 kg 15N ha−1)
was used to measure denitrification and its contribution to net N2O production
(DN2O/TN2O). BNF was measured in situ through incubation of selected sphagnum species
under 15N2 gas tracer. Denitrification2 varied temporally and averaged 8 kg N-N2
ha−1 y−1. The contribution of denitrification was about 48% to total N2O flux3 of
0.05 kg N ha−1 y−1. Soil moisture, temperature, ecosystem respiration, pH and
mineral N content mainly regulated the flux of N2 and N2O. Preliminary results
showed suppression of BNF, which was 1.8 to 7 times lower in peatland mosses
exposed to ∼15 to 20 kg N ha−1 y−1 Nr deposition in the UK than in peatland mosses
in northern Sweden with background Nr deposition. Overall, the contribution of
denitrification to Nr removal in the selected peatlands was ∼50% of the annual Nr
deposition rates, making these ecosystems vulnerable to chronic N saturation. These
results point to a need for a more comprehensive annual BNF measurement to more
accurately account for total Nr input into peatlands and its atmospheric loss due to
denitrification.
References
Sgouridis 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.
Sgouridis F and 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.
Sgouridis F and Ullah S. 2017. Environmental controls on soil greenhouse gas
(CO2, CH4, N2O) fluxes and the partitioning of N2O sources in natural and
semi-natural land use types in the UK. JGR-B (under review) |
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