 |
| Titel |
Influence of soil C stocks and interannual climatic variability on the CO2 and CH4 exchange of maize cultivated on mineral and organic soils in NE Germany |
| VerfasserIn |
Madlen Pohl, Ulrike Hagemann, Mathias Hoffmann, Michael Giebels, Elisa Albiac-Borraz, Michael Sommer, Jürgen Augustin |
| Konferenz |
EGU General Assembly 2014
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250092094
|
| Publikation (Nr.) |
 EGU/EGU2014-6419.pdf |
|
|
|
|
|
| Zusammenfassung |
| Due to its glacially influenced genesis and land use history, the soils of the Great Plain Region of NE-Germany show large differences in groundwater levels and soil carbon (C) stocks over short distances. Although generally featuring a rather dry climate, trace gas exchange at individual sites may be influenced by i) interannual climatic variability, particularly with respect to precipitation; as well as by ii) variability of soil C stocks. However, it is still unclear how these factors affect fluxes of CO2 and CH4, and if there is any positive or negative feedback on the C source or sink function of different soil types.
We present measured and modeled CO2 and CH4 fluxes of minerally fertilized grain maize for three sites located near Paulinenaue, within the so-called Rhin-Havelluch, a shallow and drained paludification mire complex in NE Germany. The sites are characterized by a distinct gradient of 0–1 m soil organic C stocks: i) Arenosol (AR: mineral soil/distant groundwater; 8 000 g C m-2), ii) Gleysol (GL: organic soil/groundwater-dependent; 35 000 g C m-2), and iii) Histosol (HS: organic soil/near groundwater; 45 000 g C m-2).
CO2 flux measurements of ecosystem respiration (Reco), net ecosystem exchange (NEE) and gross primary production (GPP; calculated as difference between NEE and Reco) were conducted every four weeks using a flow-through non-steady-state closed chamber system. Measurement gaps of Reco and NEE were filled by using temperature or radiation-based models, respectively. CH4 fluxes were measured bi-weekly using a static closed chamber system with interval sampling, with gap filling via linear interpolation. Cumulated fluxes of CO2-C (Reco, GPP, NEE) and CH4-C were calculated for a period of four consecutive years (2007–2010).
The intensity of CO2-C fluxes increased with growing soil organic C stocks (AR < GL < HS). Mean annual values of the years 2008–2010 for Reco ranged between 1 500 g C m-2 and 2 000 g C m-2; annual GPP fluxes ranged from -1 400 g C m-2 to -2 300 g C m-2. NEE balances varied from C source on the mineral AR site (65 g C m-2) to C sink for organic sites (nearly -350 g C m-2). Annual CH4 exchange rates were generally very low < 0.3 g C m-2 and negligible compared to annual CO2 exchange. However, the exceptionally wet summer of 2007 (May to July) resulted in drastically increased CH4 emissions from the groundwater-influenced organic soils, particularly at the HS site where CH4 emissions were nearly 100 times higher emissions than in the following years (28 g C m-2). The excess moisture levels in 2007 also appeared to influence ecosystem CO2 exchange – likely through effects on maize growth – resulting in strongly increased Reco and GPP rates at the mineral AR site and drastically decreased Reco and GPP rates at the flooded HS site.
The intensity of gaseous C fluxes seems to strongly depend on interactions between soil C stocks and interannual climatic variability. More detailed conclusions about the nature of these interactions require continuation of these measurements, i.e. long-term investigation. |
|
|
|
|
|
|