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| Titel |
Pulse labelling for carbon turnover measurements with a CRDS for wetlands – challenges and solutions |
| VerfasserIn |
Marcin Stróżecki, Mateusz Samson, Bogdan H. Chojnicki, Jacek Leśny, Christophe Moni, Marek Urbaniak, Janusz Olejnik, Radoslaw Juszczak, Hanna Silvennoinnen |
| 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 |
250134003
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| Publikation (Nr.) |
 EGU/EGU2016-14676.pdf |
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| Zusammenfassung |
| Carbon turnover in peatlands has commonly been studied by estimating carbon allocation and
decomposition rates by litterbags, assessing changes in carbon stocks and by measuring the
biosphere-atmosphere exchange of carbon gases with various chamber methods or by eddy
covariance. In addition, C turnover rates have been measured with pulse labelling
methods using 13C and 14C (e.g. Bahn et al. 2009). Pulse labeling (PL) studies in
wetlands are, however, sparse (e.g. Gao et al. 2015), presumably as descriptive
high water table levels and relatively low productivity render successful tracing
difficult. Quite low cost fast-gas-analyzers (Cavity Ring Down Spectrometry, CRDS)
make PL experiments more cost-worthy, but their applicability at wetland field
and further for measuring elevated 13C – levels is challenging. We carried out a
PL as a pre-experiment for a larger labelling campaign of the Wetman-project at
Rzecin wetland in Poland. We aimed at defining 1) The optimum labeling for the
peatland site, 2) The importance of dissolved 13CO2 both for the loss of the pulse label
and for the potential bias to respiratory flux, 3) The reliability of the 13CO2 and
13CH4 measurements when using dynamic closed chambers with a factory calibrated
CRDS.
We labelled the study area by a transparent chamber combined to Picarro CRDS G2201-i
(C input during labelling 4.9 μg 13C). After labelling, we monitored the respiratory 13CO2
flux and the 13CO2 content in the peat water over a 10d- period. In addition, we measured the
vegetation13C before labelling and 10 days after. Plants assimilated 2.1 μg C of the
added 13C. Half of the recovered 13CO2 (3.6 μg C) originated from respiration.
Nearly one third of added 13CO2 immediately dissolved in the water, which at the
end of the experiment retained 0.5 μg 13C. Finally, 127 % of the added label was
recovered. The high recovery was mainly caused by overestimation in the δ13C.
The results of our pre-experiment indicate that 1) Measuring dissolved gases is
required for correcting the biases to the respiratory flux 2) the Picarro CRDS has to
be thoroughly calibrated for linearity and for δ13C at different signatures. As a
result, we developed calibration methods suitable for field conditions and for higher
labels.
The Research was co-founded by the Polish National Centre for Research and
Development within the Polish-Norwegian Research Programme within the project
WETMAN (Central European Wetland Ecosystem Feedbacks to Changing Climate –
Field Scale Manipulation, Project ID: 203258, contract No. Pol-Nor/203258/31/2013
(www.wetman.pl).
Bahn, M. et al., 2009. The New phytologist,
Gao, J. et al., 2015. Scientific Reports, |
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