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| Titel |
Winter greenhouse gas fluxes (CO2, CH4 and N2O) from a subalpine grassland |
| VerfasserIn |
L. Merbold, C. Steinlin, F. Hagedorn |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 5 ; Nr. 10, no. 5 (2013-05-13), S.3185-3203 |
| Datensatznummer |
250018246
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| Publikation (Nr.) |
 copernicus.org/bg-10-3185-2013.pdf |
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| Zusammenfassung |
| Although greenhouse gas emissions during winter contribute significantly to
annual balances, their quantification is still highly uncertain in
snow-covered ecosystems. Here, carbon dioxide (CO2), methane (CH4)
and nitrous oxide (N2O) fluxes were measured at a subalpine managed
grassland in Switzerland using concentration gradients within the snowpack
(CO2, CH4, N2O) and the eddy covariance method (CO2)
during the winter 2010/2011. Our objectives were (1) to identify the
temporal and spatial variation of greenhouse gases (GHGs) and their drivers,
and (2) to estimate the GHG budget of the site during this specific season
(1 December–31 March, 121 days). Mean winter fluxes (December–March)
based on the gradient method were 0.77 ± 0.54 μmol m−2 s−1 for CO2 (1.19 ± 1.05 μmol m−2 s−1
measured by eddy covariance), −0.14 ± 0.09 nmol m−2 s−1 for CH4 and 0.23 ± 0.23 nmol m−2 s−1 for
N2O, respectively. In comparison with the CO2 fluxes measured by
eddy covariance, the gradient technique underestimated the effluxes by 50%. While CO2 and CH4 fluxes decreased with the progressing
winter season, N2O fluxes did not follow a seasonal pattern. The major
variables correlating with the fluxes of CO2 and CH4 were soil
temperature and snow water equivalent, which is based on snow height and snow
density. N2O fluxes were only explained poorly by any of the measured
environmental variables. Spatial variability across the valley floor was
smallest for CO2 and largest for N2O. During the winter season
2010/2011, greenhouse gas fluxes ranged between 550 ± 540 g CO2
m−2 estimated by the eddy covariance approach and 543 ± 247 g CO2 m−2,
−0.4 ± 0.01 g CH4 m−2 and 0.11 ± 0.1 g N2O m−2 derived by the gradient technique. Total
seasonal greenhouse gas emissions from the grassland were between 574 ± 276 and 581 ± 569 g CO2 eq. m−2, with N2O
contributing 5% to the overall budget and CH4 reducing the budget
by 0.1%. Cumulative budgets of CO2 were smaller than emissions
reported for other subalpine meadows in the Swiss Alps and the Rocky
Mountains. Further investigations on the GHG exchange of grasslands in
winter are needed in order to (1) deepen our currently limited knowledge on
the environmental drivers of each GHG, (2) to thoroughly constrain annual
balances, and (3) to project possible changes in GHG flux magnitude with
expected shorter and warmer winter periods. |
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