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| Titel |
Result of storage term measurements at a sandy grassland site |
| VerfasserIn |
Krisztina Pintér, Zoltán Barcza, János Balogh, Zoltán Nagy |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250112324
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| Publikation (Nr.) |
 EGU/EGU2015-12476.pdf |
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| Zusammenfassung |
| Eddy covariance (EC) technique is common technique to investigate fluxes over ecosystems.
In the past 20 years the focus was on the carbon dioxide (CO2) budget of ecosystems
measured as net ecosystem exchange (NEE).
Night underestimation of fluxes is a frequent problem, addressed by several EC studies.
When the turbulence is low the accumulation of CO2 close to the ground can be significant,
so the storage term (rate of change of storage, RCS) has to be taken into account. In the case
of tall vegetation storage measurements are routinely done, but in the case of short vegetation
it is often neglected based on the assumption that its positive values after sunset and
negative values at dawn extinguish each other when calculating daily and yearly
sums.
The EC system at the sandy grassland (Bugacpuszta, Hungary) was complemented by
a 5-level (0.2, 0.5, 1, 2 and 4m) concentration profile measuring system and the
storage term was calculated from the profile at half-hourly intervals. RCS was also
calculated using only the concentration measurements of the EC system assuming linear
concentration profile between the surface and the level of the measurement (linear
approach).
When comparing the uncorrected and the corrected (profile method) half-hourly fluxes
storage correction did not affect the daytime NEE values (slope=1.0084, const=-0.0053,
R2=0.9922) and had only a minor effect on the measured Reco values (slope=0.9577,
const=0.0066, R2=0.9173).
Yearly sums were calculated for the first whole year (August, 2013 - July, 2014) of the
concentration profile measurement. Application of the linear approach storage correction
enhanced the sink (more negative NEE) by 12ÂgCÂm-2Âyear-1 as compared to the
uncorrected yearly sum. On the other hand, the use of storage terms calculated from the
concentration profile measurements increased the sink activity by 54ÂgCÂm-2Âyear-1.
Considering this more than 4 fold difference, concentration profiling should also be
considered in case of grasslands when calculating storage.
Acknowledgement: Present work was supported by OTKA-PD 105944. |
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