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| Titel |
Dynamic C and N stocks – key factors controlling the C gas exchange of maize in heterogenous peatland |
| VerfasserIn |
M. Pohl, M. Hoffmann, U. Hagemann, M. Giebels, E. Albiac Borraz, M. Sommer, J. Augustin |
| 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. 9 ; Nr. 12, no. 9 (2015-05-11), S.2737-2752 |
| Datensatznummer |
250117928
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| Publikation (Nr.) |
 copernicus.org/bg-12-2737-2015.pdf |
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| Zusammenfassung |
The drainage and cultivation of fen peatlands create complex small-scale mosaics
of soils with extremely variable soil organic carbon (SOC) stocks and
groundwater levels (GWLs). To date, the significance of such sites as sources
or sinks for greenhouse gases such as CO2 and CH4 is still unclear,
especially if the sites are used for cropland. As individual control factors such as GWL fail
to account for this complexity, holistic approaches combining gas fluxes with
the underlying processes are required to understand the carbon (C) gas
exchange of drained fens. It can be assumed that the stocks of SOC and N
located above the variable GWL – defined as dynamic C and N stocks – play
a key role in the regulation of the plant- and microbially mediated CO2
fluxes in these soils and, inversely, for CH4. To test this assumption,
the present study analysed the C gas exchange (gross primary production –
GPP; ecosystem respiration – Reco; net ecosystem exchange – NEE;
CH4) of maize using manual chambers for 4 years. The study sites were
located near Paulinenaue, Germany, where we selected three soil types
representing the full gradient of GWL and SOC stocks (0–1 m) of the
landscape: (a) Haplic Arenosol (AR; 8 kg C m−2); (b) Mollic Gleysol
(GL; 38 kg C m−2); and (c) Hemic Histosol (HS; 87 kg C m−2).
Daily GWL data were used to calculate dynamic SOC (SOCdyn) and N
(Ndyn) stocks.
Average annual NEE differed considerably among sites, ranging from
47 ± 30 g C m−2 yr−1 in AR to
−305 ± 123 g C m−2 yr−1 in GL and
−127 ± 212 g C m−2 yr−1 in HS. While static SOC and N
stocks showed no significant effect on C fluxes, SOCdyn and
Ndyn and their interaction with GWL strongly influenced the C gas
exchange, particularly NEE and the GPP : Reco ratio. Moreover,
based on nonlinear regression analysis, 86% of NEE variability was
explained by GWL and SOCdyn. The observed high relevance of dynamic
SOC and N stocks in the aerobic zone for plant and soil gas exchange likely
originates from the effects of GWL-dependent N availability on C formation
and transformation processes in the plant–soil system, which promote CO2
input via GPP more than CO2 emission via Reco.
The process-oriented approach of dynamic C and N stocks is a promising,
potentially generalisable method for system-oriented investigations of the C
gas exchange of groundwater-influenced soils and could be expanded to other
nutrients and soil characteristics. However, in order to assess the climate
impact of arable sites on drained peatlands, it is always necessary to
consider the entire range of groundwater-influenced mineral and organic
soils and their respective areal extent within the soil landscape. |
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