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| Titel |
Background CH4 and N2O fluxes in low-input short rotation coppice |
| VerfasserIn |
Carolyn-Monika Görres, Terenzio Zenone, Reinhart Ceulemans |
| 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 |
250135127
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| Publikation (Nr.) |
 EGU/EGU2016-15949.pdf |
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| Zusammenfassung |
| Extensively managed short rotation coppice systems are characterized by low fluxes of CH4
and N2O. However due to the large global warming potential of these trace gases (GWP100:
CH4: 34, N2O: 298), such background fluxes can still significantly contribute to offsetting the
CO2 uptake of short rotation coppice systems. Recent technological advances in fast-response
CH4 and N2O analysers have improved our capability to capture these background fluxes, but
their quantification still remains a challenge. As an example, we present here CH4 and
N2O fluxes from a short-rotation bioenergy plantation in Belgium. Poplars have
been planted in a double-row system on a loamy sand in 2010 and coppiced in the
beginning of 2012 and 2014 (two-year rotation system). In 2013 (June – November) and
2014 (April – August), the plantation’s CH4 and N2O fluxes were measured in
parallel with an eddy covariance tower (EC) and an automated chamber system (AC).
The EC had a detection limit of 13.68 and 0.76 μmol m−2 h−1 for CH4 and N2O,
respectively. The median detection limit of the AC was 0.38 and 0.08 μmol m−2 h−1 for
CH4 and N2O, respectively. The EC picked up a few high CH4 emission events
with daily averages >100 μmol m−2 h−1, but a large proportion of the measured
fluxes were within the EC’s detection limit. The same was true for the EC-derived
N2O fluxes where the daily average flux was often close to the detection limit.
Sporadically, some negative (uptake) fluxes of N2O were observed. On the basis of the EC
data, no clear link was found between CH4 and N2O fluxes and environmental
variables. The problem with fluxes within the EC detection limit is that a significant
amount of the values can show the opposite sign, thus “mirroring” the true flux.
Subsequently, environmental controls of background trace gas fluxes might be disguised in
the analysis. As a next step, it will be tested if potential environmental drivers of
background CH4 and N2O fluxes at the plantation can be uncovered by analysing the
measurements of the AC. The majority of the fluxes captured by the AC ranged
between -2 and 2 μmol m−2 h−1 for CH4, and -0.2 and 0.2 μmol m−2 h−1 for N2O,
respectively. Understanding the environmental drivers of background CH4 and N2O
fluxes is the basis for designing reasonable gap-filling strategies, and thus for a more
accurate quantification of the contribution of these gases to the overall greenhouse
gas balance of low-input short rotation coppice systems. Additionally, it is also an
important contribution to the current debate whether soils can be significant N2O
sinks.
Funding support: ERC Advanced Grant agreement (# 233366) POPFULL under the EC
7th Framework Program (FP7/2007-2013), Flemish Hercules Foundation as Infrastructure
contract # ZW09-06, and the Methusalem Program of the Flemish Government. |
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