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| Titel |
A dynamic model of wetland extent and peat accumulation: results for the Holocene |
| VerfasserIn |
T. Kleinen, V. Brovkin, R. J. Schuldt |
| 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. 1 ; Nr. 9, no. 1 (2012-01-12), S.235-248 |
| Datensatznummer |
250006662
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| Publikation (Nr.) |
 copernicus.org/bg-9-235-2012.pdf |
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| Zusammenfassung |
Substantial deposits of peat have accumulated since the last glacial.
Since peat accumulation rates are rather low, this process was previously
neglected in carbon cycle models. For assessments of the global carbon
cycle on millennial or even longer timescales, though, the carbon
storage in peat cannot be neglected any more. We have therefore developed
a dynamic model of wetland extent and peat accumulation in order to
assess the influence of peat accumulation on the global carbon cycle.
The model is based on the dynamic global vegetation model LPJ and
consists of a wetland module and routines describing the accumulation
and decay of peat. The wetland module, based on the TOPMODEL approach,
dynamically determines inundated area and water table, which change
depending on climate. Not all temporarily inundated areas accumulate
peat, though, but peat accumulates in permanently inundated areas
with rather stable water table position. Peatland area therefore is
highly uncertain, and we perform sensitivity experiments to cover
the uncertainty range for peatland extent. The peat module describes
oxic and anoxic decomposition of organic matter in the acrotelm, i.e.,
the part of the peat column above the permanent water table, as well
as anoxic decomposition in the catotelm, the peat below the summer
minimum water table.
We apply the model to the period of the last 8000 years, during which
the model accumulates 330 PgC as catotelm peat in the peatland areas
north of 40° N, with an uncertainty range from 240 PgC
to 490 PgC. This falls well within the range of published estimates
for the total peat storage in high northern latitudes, considering
the fact that these usually cover the total carbon accumulated, not
just the last 8000 years we considered in our model experiments. In
the model, peat primarily accumulates in Scandinavia and eastern Canada,
though eastern Europe and north-western Russia also show substantial
accumulation. Modelled wetland distribution is biased towards Eurasia,
where inundated area is overestimated, while it is underestimated
in North America. Latitudinal sums compare favourably to measurements,
though, implying that total areas, as well as climatic conditions
in these areas, are captured reasonably, though the exact positions
of peatlands are not modelled well. Since modelling the initiation
of peatland growth requires a knowledge of topography below peat deposits,
the temporal development of peatlands is not modelled explicitly,
therefore overestimating peatland extent during the earlier part of
our experiments.
Overall our results highlight the substantial amounts of carbon taken
up by peatlands during the last 8000 years. This uptake would have
substantial impacts on the global carbon cycle and therefore cannot
be neglected. |
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