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| Titel |
Detecting management and fertilization effects on the carbon balance of
winter oilseed rape with manual closed chamber measurements: Can we outrange
gap-filling uncertainty and spatiotemporal variability? |
| VerfasserIn |
Vytas Huth, Antje Maria Moffat, Anna Calmet, Monique Andres, Judit Laufer, Natalia Pehle, Bernd Rach, Laura Gundlach, Jürgen Augustin |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250151291
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| Publikation (Nr.) |
 EGU/EGU2017-15855.pdf |
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| Zusammenfassung |
| Winter oilseed rape is the dominant biofuel crop in the young moraine landscape in
North-Eastern Germany. However, studies on the effect of rapeseed cropping on net
ecosystem exchange of CO2 (NEE) and the soil carbon (SC) balance are scarce. SC
balance estimates are usually derived from long-term soil sampling field trials where
rapeseed is part of different crop rotations. The estimated annual differences linked
to rapeseed cropping are rather small (varying between losses of 40 g C m−2
and gains of up to 100 g C m−2). Testing management effects on the NEE and
SC balance of cropping systems is best done by comparing plots with different
treatments at the same site under the same climate. The soil sampling approach is
in the need of field trials that run over decades, which has the disadvantage that
management strategies of practical farming may have already changed when the results are
derived. Continuous eddy covariance measurements of NEE would require large
fields in flat terrain for each of the treatments, which is especially complicated
in the heterogeneous landscapes of glacigenic origin of North-Eastern Germany.
The common approach of using the chamber technique to derive NEE, however, is
subject to the local soil and plant stand heterogeneities due to its tiny footprint. This
technique might also disturb the ecosystem, the measurements are usually discontinuous
requiring elaborate gap-filling techniques, and it has mostly been used on organic
soils where large respiratory C losses occur. Therefore, our aim was to answer, if a
combined approach of the eddy covariance and the chamber technique can detect the
relatively small NEE and SC differences of rapeseed cropping on mineral soils
within a shorter period of time than conventional soil sampling field trials can. We
tested the new experimental design taking the advantages of both techniques into
account: The eddy covariance tower measuring the NEE dynamics during the year; the
chamber measurements to detect the flux differences between specific management
practices - with additional chamber measurements installed close to the eddy tower as a
reference linking the two techniques. In our experiment, we studied the effect of four
different treatments of fertilization (mineral versus organic) and tillage (no-till versus
mulch-till versus ploughing) on the NEE of rapeseed cropping for the climatic seasons
2013 to 2015. We compared the NEE of the treatments to the “background” NEE
measured by the eddy covariance technique in the nearby reference field for the years
2013 and 2014. With this data, we estimated the uncertainty resulting from gap
filling discontinuous chamber measurements and relate it to the observed effects
of the four different treatments on the NEE. Here, we present first results on the
applicability of the manual-chamber technique to derive the relatively small effects of
rapeseed cropping on NEE and SC within a short period of three years of study. |
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