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| Titel |
Global soil nitrous oxide emissions in a dynamic carbon-nitrogen model |
| VerfasserIn |
Y. Huang, S. Gerber |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 21 ; Nr. 12, no. 21 (2015-11-10), S.6405-6427 |
| Datensatznummer |
250118158
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| Publikation (Nr.) |
 copernicus.org/bg-12-6405-2015.pdf |
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| Zusammenfassung |
| Nitrous oxide (N2O) is an important greenhouse gas that also
contributes to the depletion of stratospheric ozone. Due to its high
temporal and spatial heterogeneity, a quantitative understanding of
terrestrial N2O emission and its variabilities and responses to climate
change are challenging. We added a soil N2O emission module to the
dynamic global land model LM3V-N, and tested its sensitivity to mechanisms
that affect the level of mineral nitrogen (N) in soil such as plant N
uptake, biological N fixation, amount of volatilized N redeposited after
fire, and nitrification-denitrification. We further tested the relationship
between N2O emission and soil moisture, and assessed responses to
elevated CO2 and temperature. Results extracted from the corresponding
gridcell (without site-specific forcing data) were comparable with the
average of cross-site observed annual mean emissions, although differences
remained across individual sites if stand-level measurements were
representative of gridcell emissions. Processes, such as plant N uptake and
N loss through fire volatilization that regulate N availability for
nitrification-denitrification have strong controls on N2O fluxes in
addition to the parameterization of N2O loss through nitrification and
denitrification. Modelled N2O fluxes were highly sensitive to water-filled pore space (WFPS), with a global sensitivity of approximately 0.25 TgN per year per 0.01 change in WFPS. We found that the global response of
N2O emission to CO2 fertilization was largely determined by the
response of tropical emissions with reduced N2O fluxes in the first few
decades and increases afterwards. The initial reduction was linked to N
limitation under higher CO2 level, and was alleviated through feedbacks
such as biological N fixation. The extratropical response was weaker and
generally positive, highlighting the need to expand field studies in
tropical ecosystems. We did not find synergistic effects between warming and
CO2 increase as reported in analyses with different models. Warming
generally enhanced N2O efflux and the enhancement was greatly dampened
when combined with elevated CO2, although CO2 alone had a small
effect. The differential response in the tropics compared to extratropics
with respect to magnitude and sign suggests caution when extrapolating from
current field CO2 enrichment and warming studies to the globe. |
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