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| Titel |
Stomata-controlled nighttime COS fluxes in a boreal forest: implications for the use of COS as a GPP tracer |
| VerfasserIn |
Linda M. J. Kooijmans, Kadmiel Maseyk, Ulli Seibt, Timo Vesala, Ivan Mammarella, Ian T. Baker, Alessandro Franchin, Pasi Kolari, Wu Sun, Helmi Keskinen, Janne Levula, Huilin Chen |
| 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 |
250132673
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| Publikation (Nr.) |
 EGU/EGU2016-13203.pdf |
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| Zusammenfassung |
| Carbonyl Sulfide (COS) is a promising new tracer that can be used to partition the Net
Ecosystem Exchange into gross primary production (GPP) and respiration. COS and CO2
vegetation fluxes are closely related as these gases share the same diffusion pathway into
stomata. This close coupling is the fundamental principle for the use of COS as tracer
for GPP. Nonetheless, in contrast to CO2 , the uptake of COS by vegetation is not
light-dependent, and therefore the vegetative uptake of COS can continue during the night as
long as stomata are open. Nighttime stomatal conductance is observed in a variety of studies,
and also nighttime depletion of COS concentrations is reported several times but it is not
confirmed with field measurements that the depletion of COS in the night is indeed driven by
stomatal opening. In the summer of 2015 a campaign took place at the SMEAR II site in
Hyytiälä, Finland to provide better constrained COS flux data for boreal forests using a
combination of COS measurements, i.e. atmospheric profile concentrations up to 125 m,
eddy-covariance fluxes and soil chamber fluxes, and collocated measurements of
stomatal conductance and 222Radon. A high correlation between concentrations of
222Radon and COS implies that the radon-tracer method is a valuable tool to derive
nighttime ecosystem COS fluxes. We find that soils contribute to 17% of the total
ecosystem COS flux during nighttime in the peak growing season. Nighttime ecosystem
COS fluxes show a correlation with stomatal conductance (R2 = 0.3), indicating
that nighttime COS fluxes are primarily driven by vegetation. The COS vegetation
fluxes will be compared with calculated fluxes from the Simple Biosphere model.
Furthermore, the nighttime vegetative COS uptake covers a substantial fraction
(25%) of the daily maximum COS uptake by vegetation. Accurate quantification of
nighttime COS uptake is required to be able to use COS as a useful tracer for GPP. |
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