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| Titel |
Uncertainties in modelling CH4 emissions from northern wetlands in glacial climates: the role of vegetation parameters |
| VerfasserIn |
C. Berrittella, J. Huissteden |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 7, no. 4 ; Nr. 7, no. 4 (2011-10-11), S.1075-1087 |
| Datensatznummer |
250004675
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| Publikation (Nr.) |
 copernicus.org/cp-7-1075-2011.pdf |
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| Zusammenfassung |
Marine Isotope Stage 3 (MIS 3) interstadials are marked by a sharp increase
in the atmospheric methane (CH4) concentration, as recorded in ice
cores. Wetlands are assumed to be the major source of this CH4,
although several other hypotheses have been advanced. Modelling of CH4
emissions is crucial to quantify CH4 sources for past climates.
Vegetation effects are generally highly generalized in modelling past and
present-day CH4 fluxes, but should not be neglected. Plants strongly
affect the soil-atmosphere exchange of CH4 and the net primary
production of the vegetation supplies organic matter as substrate for
methanogens. For modelling past CH4 fluxes from northern wetlands,
assumptions on vegetation are highly relevant since paleobotanical data
indicate large differences in Last Glacial (LG) wetland vegetation
composition as compared to modern wetland vegetation. Besides more
cold-adapted vegetation, Sphagnum mosses appear to be much less dominant during
large parts of the LG than at present, which particularly affects CH4
oxidation and transport. To evaluate the effect of vegetation parameters, we
used the PEATLAND-VU wetland CO2/CH4 model to simulate emissions
from wetlands in continental Europe during LG and modern climates.
We tested the effect of parameters influencing oxidation during plant
transport (fox), vegetation net primary production (NPP, parameter
symbol Pmax), plant transport rate (Vtransp), maximum rooting depth
(Zroot) and root exudation rate (fex). Our model results show that
modelled CH4 fluxes are sensitive to fox and Zroot in
particular. The effects of Pmax, Vtransp and fex are of lesser
relevance. Interactions with water table modelling are significant for
Vtransp.
We conducted experiments with different wetland vegetation types for Marine
Isotope Stage 3 (MIS 3) stadial and interstadial climates and the
present-day climate, by coupling PEATLAND-VU to high resolution climate
model simulations for Europe. Experiments assuming dominance of one
vegetation type (Sphagnum vs. Carex vs. Shrubs) show that Carex-dominated vegetation can increase
CH4 emissions by 50% to 78% over Sphagnum-dominated vegetation depending
on the modelled climate, while for shrubs this increase ranges from 42%
to 72%. Consequently, during the LG northern wetlands may have had
CH4 emissions similar to their present-day counterparts, despite a
colder climate. Changes in dominant wetland vegetation, therefore, may drive
changes in wetland CH4 fluxes, in the past as well as in the future. |
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