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| Titel |
Modelling contrasting responses of wetland productivity to changes in water table depth |
| VerfasserIn |
R. F. Grant, A. R. Desai, B. N. Sulman |
| 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 ; 9, no. 11 ; Nr. 9, no. 11 (2012-11-01), S.4215-4231 |
| Datensatznummer |
250007371
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| Publikation (Nr.) |
 copernicus.org/bg-9-4215-2012.pdf |
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| Zusammenfassung |
| Responses of wetland productivity to changes in water table depth (WTD) are
controlled by complex interactions among several soil and plant processes,
and hence are site-specific rather than general in nature. Hydrological
controls on wetland productivity were studied by representing these
interactions in connected hummock and hollow sites in the ecosystem model
ecosys, and by testing CO2 and energy fluxes from the model with those
measured by eddy covariance (EC) during years with contrasting WTD in a
shrub fen at Lost Creek, WI. Modelled interactions among coupled processes
for O2 transfer, O2 uptake, C oxidation, N mineralization, N
uptake and C fixation by diverse microbial, root and mycorrhizal populations
enabled the model to simulate complex responses of CO2 exchange to
changes in WTD that depended on the WTD at which change was occurring. At
the site scale, greater WTD caused the model to simulate greater CO2
influxes and effluxes over hummocks vs. hollows, as has been found at field
sites. At the landscape scale, greater WTD caused the model to simulate
greater diurnal CO2 influxes and effluxes under cooler weather when
water tables were shallow, but also smaller diurnal CO2 influxes and
effluxes under warmer weather when water tables were deeper, as was also
apparent in the EC flux measurements. At an annual time scale, these diurnal
responses to WTD in the model caused lower net primary productivity (NPP)
and heterotrophic respiration (Rh), but higher net ecosystem
productivity (NEP = NPP − Rh), to be simulated in a cooler year with a
shallower water table than in a warmer year with a deeper one. This
difference in NEP was consistent with those estimated from gap-filled EC
fluxes in years with different water tables at Lost Creek and at similar
boreal fens elsewhere. In sensitivity tests of the model, annual NEP
declined with increasing WTD in a year with a shallow water table, but rose
in a year with a deeper one. The model thus provided an integrated set of
hypotheses for explaining site-specific and sometimes contrasting responses
of wetland productivity to changes in WTD as found in different field
experiments. |
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