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| Titel |
Are microbial N transformation rates in a permanent grassland soil after 17 years of elevated atmospheric CO2 sensitive to soil temperature? |
| VerfasserIn |
Gerald Moser, Andre Gorenflo, Kristof Brenzinger, Tim Clough, Gesche Braker, Christoph Müller |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250133466
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| Publikation (Nr.) |
 EGU/EGU2016-14079.pdf |
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| Zusammenfassung |
| Long-term observations (17 years) within the Giessen Free Air Carbon dioxide Enrichment
(Giessen FACE) study on permanent grassland showed that the carbon fertilization caused
significant changes in the ecosystem nitrogen cycle. These changes are responsible
for a doubling of annual N2O emissions under elevated atmospheric CO2 (eCO2)
caused by increased emissions during the plant growing season. The goal of this lab
study was to understand how soil temperature influences the long-term effects of
eCO2 and plant carbon input on microbial N transformations in the Giessen FACE.
Therefore, a pulse labelling study with 15N tracing of 15NH4+ and 15NO3− was
carried out with incubated soil samples from elevated and ambient CO2 FACE
rings in climate chambers at two different temperatures (10∘C and 19∘C), while
water filled pore space of the samples was adjusted to the same level. The various N
pools in the soil (NH4+, NO3−, NO2−, soil organic matter), N2O emissions and
simultaneous gross N transformation rates were quantified. The quantification of the
gross N transformations are based on the turnover of 15NH4+, 15NO3−, 15NO2−
and shall illuminate the interaction between carbon fertilization, temperature and
changes in nitrogen cycle in this grassland soil. While the soil respiration after
labelling was significantly increased at 19∘C compared to 10∘C, N2O emissions
showed no significant differences. There were also no significant differences of N2O
emissions between soil samples from control and elevated CO2 rings within each
temperature level. As the soil temperature (within the range of 10-19∘C) had no
significant effects on N transformations responsible for the observed doubling of N2O
emissions under eCO2, it seems most likely that other factors like direct carbon input
by plants and/or soil moisture differences between ambient and elevated rings in
the field are responsible for the observed increase in N2O emissions under eCO2. |
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