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| Titel |
Modeling Complex Water Table Effects on Net CO2 Exchange of Western Canadian Peatlands |
| VerfasserIn |
Mohammad Mezbahuddin, Robert Grant, Lawrence Flanagan |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250072992
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| Zusammenfassung |
| Water table fluctuation is one of the key controls governing peatland carbon balance under
current and future climatic conditions. Seasonal and inter-annual variations in water
table depths can alter the balance between peatland primary production and respiration and
so cause a peatland to change between a sink and a source of carbon. Water table fluctuations
can affect primary production and respiration through its influence on evapotranspiration,
plant water and nutrient uptake and on microbial decomposition. Simulating water table
effects on current and future net ecosystem productivity (NEP) of peatlands thus
demands models with coupled soil-plant-atmosphere schemes for gases, water,
energy, carbon and nutrients (N, P). We combined a 3-dimensional water transport
scheme and prognostic water table dynamics with an existing ecosystem model
ecosys in order to examine the water table effects on seasonal and inter-annual
variability in NEP of a moderately rich fen peatland in Alberta, Canada. Simulated
hourly ecosystem energy and CO2 fluxes along with hourly water table depths
correlated very well (R2 ~ 0.75) with measurements at the site from 2003 to
2009, during which the water table declined gradually. We compared modeled and
measured fluxes at hourly and seasonal time scales in years with contrasting water table
depths in order to see how water table fluctuations altered the diurnal and seasonal
patterns of NEP. In the model, shallow water tables limited root and soil aeration,
slowing root and microbial growth, and hence nutrient uptake. This reduced gross
primary productivity (GPP) but also ecosystem respiration (RE), so that the peatland
remained a substantial net carbon sink. In the model, deeper water tables caused more
rapid microbial and root growth, and hence more rapid mineralization and nutrient
uptake, and hence greater GPP. Deeper water tables also caused near-surface drying
which slightly reduced near surface peat decomposition. However this reduction was
offset by more rapid decomposition in deeper peat layers so that total RE increased.
Concurrent increases in GPP and RE caused simulated and measured NEP to change in
complex ways with deeper water tables. These complex changes in seasonal and
annual CO2exchange with changes in hydrology can be simulated with models that represent
basic processes for soil-plant-atmosphere transfers of gases, particularly O2, as well as
those of water and energy. Such models can provide a predictive capability for
how peatland productivity might change with hydrology under future climates. |
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