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| Titel |
Peat decomposition indicators of two contrasting peat bogs in the Eastern Alps, Austria |
| VerfasserIn |
Simon Drollinger, Yakov Kuzyakov, Stephan Glatzel |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250151782
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| Publikation (Nr.) |
 EGU/EGU2017-16540.pdf |
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| Zusammenfassung |
| Worldwide ∼612 Pg of carbon (C) is stored in peat, of which ∼270 to 370 Pg C have been
removed from the atmosphere by peat growth since the last glacial period. Since C in
peatlands is labile and sensitive to disturbances, peatlands entail the potential to release high
amounts of C in the course of land use changes and proceeding global warming. Therefore,
adequate peat decomposition indicators (PDI) are necessary to assess the peatland
degradation status and potential C release of peatlands.
In order to assess the degradation status of Alpine peat bogs and to evaluate the PDI, we
compare PDI in two Alpine peat bogs with contrasting land-use histories located in
the Enns valley, Austria. We evaluate the conventional PDI loss on ignition, bulk
density, C:N ratios, water table depths (WTD) and the recently introduced PDI stable
carbon isotope ratios (δ13C) and stable nitrogen isotope ratios (δ15N) at nine study
sites.
We detected significant differences in PDI between the two bogs and between the study
sites, which vary in WTD and degree of decomposition. Moreover, we demonstrate strong
relationships and similar depth profiles of the variables. Loss on ignition of strongly degraded
sites decrease from the acrotelm (94.77%) to the catotelm (80.02%), but remain stable at less
degraded sites (∼97.76%). Bulk density generally increases with depth, featuring lowest
values in the acrotelm of the central bog area (0.05 g cm−3) and highest values in the
catotelm of the former peat cutting areas (0.18 g cm−3). C:N ratios exhibit large variations at
most sites, but demonstrate differences in the degree of decomposition. Regarding the
δ13C and δ15N, we observed an increase in the uppermost layers down to depths
of -24 to -42 cm at all study sites. In the catotelm, δ13C are significantly lower
in strongly decomposed peat (-27.44 ±0.37‰) in contrast to the less degraded
sites (-26.09 ±0.59‰). δ15N are significantly higher at strongly degraded sites in
both, acrotelm (-0.75 ±2.11‰) and catotelm (-0.45 ±0.84‰) compared to the
slightly degraded sites (-4.89 ±1.91‰ and -4.37 ±1.10‰ respectively). C isotope
discrimination in plants causes a depletion in δ13C of the residual litter, as 13C is more
frequent in polysaccharides, representing the easier decomposable component of
the litter. In contrast, aerobic decomposers tend to preferably use 12C and during
respiration, resulting in a relative enrichment of 13C in the residual organic matter.
Accordingly, the increase of δ13C in the acrotelm in strong decayed peat are assigned
to the respiration process, whereas the preferential removal of polysaccharides is
the dominating fractionation mechanism in the catotelm of the strongly degraded
sites.
We conclude that the PDI are partially comparable and that it is possible to assess the
degradation status of the respective sites. The use of δ15N and δ13C as PDI is implementable,
but with limitations: slight differences in the degree of peat decomposition could not be
revealed and initial ratios of different plant species and atmospheric ratios during peat
formation may differ widely. |
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