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| Titel |
Greenhouse gas balances of managed peatlands in the Nordic countries – present knowledge and gaps |
| VerfasserIn |
M. Maljanen, B. D. Sigurdsson, J. Guðmundsson, H. Óskarsson, J. T. Huttunen, P. J. Martikainen |
| 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 ; 7, no. 9 ; Nr. 7, no. 9 (2010-09-15), S.2711-2738 |
| Datensatznummer |
250004967
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| Publikation (Nr.) |
 copernicus.org/bg-7-2711-2010.pdf |
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| Zusammenfassung |
| This article provides an overview of the effects of land-use on the fluxes
of carbon dioxide (CO2), methane (CH4) and nitrous oxide
(N2O) and from peatlands in the Nordic countries based on the field
data from about 100 studies. In addition, this review aims to identify the
gaps in the present knowledge on the greenhouse gas (GHG) balances
associated with the land-use of these northern ecosystems. Northern
peatlands have accumulated, as peat, a vast amount of carbon from the
atmosphere since the last glaciation. However, the past land-use and present
climate have evidently changed their GHG balance. Unmanaged boreal peatlands
may act as net sources or sinks for CO2 and CH4 depending on the
weather conditions. Drainage for agriculture has turned peatlands to
significant sources of GHGs (mainly N2O and CO2). Annual mean GHG
balances including net CH4, N2O and CO2 emissions are 2260,
2280 and 3140 g CO2 eq. m−2 (calculated using 100 year time
horizon) for areas drained for grass swards, cereals or those left fallow,
respectively. Even after cessetion of the cultivation practices, N2O
and CO2 emissions remain high. The mean net GHG emissions in abandoned
and afforested agricultural peatlands have been 1580 and 500 g CO2 eq. m−2,
respectively. Peat extraction sites are net sources of GHGs with
an average emission rate of 770 g CO2 eq. m−2. Cultivation of a
perennial grass (e.g., reed canary grass) on an abandoned peat extraction
site has been shown to convert such a site into a net sink of GHGs
(−330 g CO2 eq. m−2). In contrast, despite restoration, such sites are
known to emit GHGs (mean source of 480 g CO2 eq. m−2, mostly from
high CH4 emissions). Peatland forests, originally drained for forestry,
may act as net sinks (mean −780 g CO2 eq. m−2). However, the
studies where all three GHGs have been measured at an ecosystem level in the
forested peatlands are lacking. The data for restored peatland forests
(clear cut and rewetted) indicate that such sites are on average a net sink
(190 g CO2 eq. m−2). The mean emissions from drained peatlands
presented here do not include emissions from ditches which form a part of
the drainage network and can contribute significantly to the total GHG
budget. Peat soils submerged under water reservoirs have acted as sources of
CO2, CH4 and N2O (mean annual emission 240 g CO2 eq. m−2).
However, we cannot yet predict accurately the overall greenhouse
gas fluxes of organic soils based on the site characteristics and land-use
practices alone because the data on many land-use options and our
understanding of the biogeochemical cycling associated with the gas fluxes
are limited. |
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