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| Titel |
Effect of N-fertilization on N2 and N2O flux rates in relation to the structure of the denitrifying bacterial community in fen soil |
| VerfasserIn |
J. Augustin, U. Behrendt, A. Ulrich |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250031538
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| Zusammenfassung |
| Drained fen peatlands of north-east Europe managed by different agricultural regimes
constitute an important source for emissions of nitrous oxide (N2O) into the atmosphere. The
strength of N2O fluxes showed a high variability in time and space influenced by complex
interactions of formation and transfer processes with environmental parameters which makes
prediction of emissions uncertain. This applies particularly to the denitrification. This is one
of the microbial processes with special interest for N2O production in the context
of frequently varying soil-moisture content of fen soils that favouring anaerobic
conditions. Moreover, denitrification may result in the production of both N2O and N2
in varying proportions. However, not only the knowledge about the effect of soil
chemical and physical properties, climate, vegetation, and management on the actual
N2O and N2 fluxes is very incomplete at fen soils. There are also no information
about the role of structure and activity of denitrifying microbial communities in
this context either. The experiments presented in this study aim at addressing this
subject matter. Relatively undisturbed soil columns (250 cm3) from a long-term
N-fertilization experiment on a fen grassland (over a period of 45 years) were used for
measurement of the current N2 and N2O fluxes followed by processing the soil sample for
microbiological analysis immediately to investigate the influence of N-fertilization on these
parameters.
The direct measurement of N2 and N2O fluxes was performed by a helium atmosphere
incubation technique in the lab. Results showed a strong influence of N-fertilization
and soil moisture on the emission of N2 and N2O. Shifts in the total microbial
community were estimated by phospholipid fatty acid analysis, a fingerprint focused on
active organisms. Results showed that seasonal effects interfered the influence of
N-fertilization on shifts of the total microbial community composition. To characterise
the denitrifying bacterial community, a combination of cultivation (screening and
isolation) and cultivation-independent methods targeting different enzymes of the
denitrification process were used. In addition to selective cultivation the abundance of
denitrifying bacteria was studied by a real-time PCR approach quantifying the nitrite
reductase (nirK) and the nitrous oxide reductase (nosZ) genes. Results of both methods
demonstrated only a marginal effect on the abundance of this functional group.
The analysis of the community structure of denitrifying bacteria was performed by
cultivation under selective conditions, physiological tests of the isolates and their
phylogenetic assignment. In parallel, the community structure was studied by a nirK
clone library. In contrast to the abundance of the nirK and nosZ genes, both the
composition of the isolates as well as the cloning approach revealed a long-term effect of
N-fertilization.
The results show clearly that the combination of different experimental approaches can
actually lead to a better understanding of the N turnover and loss processes of fen peatlands. |
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