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| Titel |
Quantifying wetland methane emissions with process-based models of different complexities |
| VerfasserIn |
J. Tang, Q. Zhuang, R. D. Shannon, J. R. White |
| 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 ; 7, no. 11 ; Nr. 7, no. 11 (2010-11-25), S.3817-3837 |
| Datensatznummer |
250005072
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| Publikation (Nr.) |
 copernicus.org/bg-7-3817-2010.pdf |
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| Zusammenfassung |
| Bubbling is an important pathway of methane emissions from wetland
ecosystems. However the concentration-based threshold function
approach in current biogeochemistry models of methane is not
sufficient to represent the complex ebullition process. Here we revise
an extant process-based biogeochemistry model, the Terrestrial
Ecosystem Model into a multi-substance model (CH4, O2,
CO2 and N2) to simulate methane production, oxidation, and
transport (particularly ebullition) with different model
complexities. When ebullition is modeled with a concentration-based
threshold function and if the inhibition effect of oxygen on methane
production and the competition for oxygen between methanotrophy and
heterotrophic respiration are retained, the model becomes a two-substance
system. Ignoring the role of oxygen, while still modeling ebullition
with a concentration-based threshold function, reduces the model to
a one-substance system. These models were tested through a group of
sensitivity analyses using data from two temperate peatland sites in Michigan. We
demonstrate that only the four-substance model with a pressure-based
ebullition algorithm is able to capture the episodic emissions induced
by a sudden decrease in atmospheric pressure or by a sudden drop in water table.
All models captured the retardation effect on methane efflux from
an increase in surface standing water which results from the inhibition
of diffusion and the increase in rhizospheric oxidation. We conclude that to more
accurately account for the effects of atmospheric pressure dynamics
and standing water on methane effluxes, the multi-substance model with
a pressure-based ebullition algorithm should be used in the future to
quantify global wetland CH4 emissions. Further, to more
accurately simulate the pore water gas concentrations and different
pathways of methane transport, an exponential root distribution
function should be used and the phase-related parameters should be
treated as temperature dependent. |
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