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| Titel |
Only low methane production and emission in degraded peat extraction sites after rewetting |
| VerfasserIn |
Svenja Agethen, Carolin Waldemer, Klaus-Holger Knorr |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250113089
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| Publikation (Nr.) |
 EGU/EGU2015-13286.pdf |
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| Zusammenfassung |
| In Central Europe rewetting of bogs after peat extraction is a wide spread technique to halt
secondary aerobic decomposition and to reestablish plant species such as Sphagnum spp. and
Eriophorum spp. that initialize accumulation of organic carbon in peat. Before
extraction, such sites are often used for agriculture causing the aerobic degradation
of peat and mobilization of phosphorus, ammonia, and dissolved organic matter
(DOM). In nutrient poor ecosystems such as bogs, additional supply of P and N
does not only trigger the establishment of uncharacteristic vegetation but also the
formation of more labile plant litter and DOM that is readily degradable. Therefore,
after rewetting and the development of anoxic conditions especially in initial stages
high methane (CH4) emissions are reported for these systems compared to pristine
bogs.
Regarding the potential of methane production and emissions we investigated three
common practices to prepare extraction fields for restoration (years since rewetting): i) Filling
of drainage ditches, passive rewetting (1 site, Altendorfer Moor, Stade, NW-Germany, ca. 20
yr.), ii) Removal of upper 30 cm peat layer, removed peat used for construction of polder
dikes (2 sites, Königsmoor, Leer, NW-Germany, 2 and 3 yr.), iii) Removal upper peat
layer down to 50 cm grown peat, not extracted peat used as polder walls (2 sites,
Benthullener Moor, Wardenburg, NW-Germany, 3 and 7 yr.). In each site two vegetated
replicate mesocosms (diam. 30 cm, depth 40 cm) were sampled and placed in a
greenhouse from May-October 2014 to maintain the water table at surface level.
Pore water concentrations of ions, fermentation products and DOM, DOM electron
acceptor capacity (EAC), soil gas concentrations of CO2, CH4 and H2, gas fluxes as
well as element composition and organic matter quality of DOM and SOM were
analyzed.
We found out that practice i) with least efforts of nutrient removal in the peat produced
the highest CH4 emissions (3.5 mmol m-2 d-1) although still within the range of
northern pristine bogs. Also practice ii) showed still inputs of external nutrients and
labile DOM, but CH4 production was not yet developed (0.23 and 0.07 mmol m-2
d-1). Practice iii) was most effective in nutrient removal, but only in the 7 yr. site
little methane (in the 3 yr. site 0.025 vs. 0.41 mmol m-2 d-1in the 7 yr. site) was
emitted. The emissions were well in accord with soil gas concentrations, maximum
values for CH4 in practice i) were 115 μmol L-1, 2-5 μmol L-1 in practice ii)
and 0.5 vs. 16 μmol L-1 in practice iii). Only small concentrations of inorganic
electron acceptors such as sulfate imply the importance of organic matter as electron
acceptor.
The results show that restored bogs on former strongly degraded extraction fields do not
necessarily act as exceptionally high CH4 sources. Contrary to other findings in early stages
of rewetting CH4 emissions can also be very low until other electron acceptors are exhausted
and methanogens become effective competitors for substrates which happens in the order of
years. |
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