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| Titel |
The role of plant functional groups in methane dynamics in a boreal fen under pristine and water level drawdown conditions |
| VerfasserIn |
T. Riutta, E.-S. Tuittila, J. Laine |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250069757
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| Zusammenfassung |
| Vegetation and hydrology are important controlling factors in peatland methane dynamics.
Vegetation structures (i.e. species composition, physiognomy, density) and productivity
are strongly interlinked with moisture conditions (water table level variation), and
the methane flux is a result of the vegetation-water table interaction, rather than a
direct effect of water table or vegetation. Therefore, observational studies in pristine
peatlands have a limited ability to separate the effects of these factors. This study
aimed to experimentally quantify the role of the fen ecosystem components —
sedges, dwarf shrubs, Sphagnum mosses, and the underlying peat — in methane
fluxes in control and experimental water table drawdown conditions and to separate
the plant-mediated effects from the effect of altered water table level on methane
fluxes.
We carried out the experiment in a boreal nutrient-poor fen using two treatments: a
vegetation component removal treatment with four levels and a water level treatment with
two levels (control and a 15 cm water level draw down). We measured methane fluxes during
four growing seasons using a static chamber technique. The first year was a calibration season
preceding the water level drawdown treatment. Based on the vegetation removal treatments,
plant-mediated fluxes comprised 75% of the total cumulative growing season methane flux
(7.8 ± 0.83 g CH4 m-2 from June to September) in the control water level conditions.
Sedge and Sphagnum moss mediated fluxes accounted for 48% and 27% of the
total flux, respectively. The presence of dwarf shrubs, on the other hand, had a
slightly attenuating effect on the fluxes. In water level drawdown conditions, fluxes
were significantly lowered (cumulative growing season flux 0.12 ± 0.10 g CH4
m-2) and the presence / absence of the plant groups had hardly any effect on the
fluxes. There was a tight, positive relationship between net ecosystem production
and methane flux in the control conditions but not in the water level drawdown
conditions, where the methane fluxes showed very little spatial or temporal variation.
In conclusion, water level acts as a switch; only after passing through the water
level control does the vegetation regulate the fluxes. The results are relevant for
assessing the response of peatland fluxes in changing climatic conditions, as water level
drawdown is the major projected impact of climate change on northern peatlands. |
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