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| Titel |
Estimates of net ecosystem productivity at Jastrebarsko forest eddy covariance site in comparison with other forest sites in FLUXNET |
| VerfasserIn |
Hrvoje Marjanović, Masa Zorana Ostrogovic, Giorgio Alberti, Ivan Balenovic, Alessandro Peressotti |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250057040
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| Zusammenfassung |
| Net Ecosystem Productivity (NEP) of 35-year-old pedunculate oak (Quercus robur L.) stand
was investigated during 2008 and 2009 at eddy covariance (EC) site located in Jastrebarsko
pedunculate oak forest, currently undergoing the process of joining FLUXNET network. Two
independent methods for assessing NEP were used: 1) eddy covariance; and 2) the
"combined" method, using difference between Net Primary Productivity (NPP), assessed with
biometric measurements, and heterotrophic respiration (Rh) estimated from soil respiration
(SR) measurements.
Maximal measured daily NEP from eddy covariance was 10,7 gC m-2 day-1 in 2008.,
and 12,2 gC m-2 day-1 in 2009. The annual NEP ranged from 384 gC m-2 yr-1 in 2008 to
584 gC m-2 yr-1 in 2009 indicating that the stands around the tower were actively storing
carbon during both years.
Using weekly measurements of stem increment on 640 dendrometer bands, annual height
increment and litter production we obtained an estimate of the NPP of the stands in the
footprint of 777 gC m-2 yr-1 in 2008 and 846 gC m-2 yr-1 in 2009. Heterotrophic
respiration (Rh) , estimated from soil respiration measurements was 438 gC m-2 yr-1 in
2008 and 441 gC m-2 yr-1 in 2009. By subtracting Rh from NPP, we obtained NEP of 339
and 405 gC m-2 yr-1 in 2008 and 2009, respectively.
Comparison of results for NEP during vegetation season reveals that agreement between
the two methods was very good until July. Later in the summer and autumn, discrepancy
occurs when stem growth ceases but trees continue to actively store carbon. This leads to
the underestimation of NEP from combined method during that period, leading
to the overall lower values of NEP when compared with NEP values from eddy
covariance.
Results of our measurements are compared with other forest sites in FLUXNET
network.
Further research is needed that would provide better estimates of Rh, R:S ratio, and
related uncertainties in carbon fluxes in pedunculate oak forests. |
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