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| Titel |
The role of \textit{Juncus effusus} litter quality and nutrient availability on organic matter
decomposition in restored cutover bogs |
| VerfasserIn |
Svenja Agethen, Klaus-Holger Knorr |
| 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 |
250150628
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| Publikation (Nr.) |
 EGU/EGU2017-15106.pdf |
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| Zusammenfassung |
| More than 90% of peatlands in Europe are degraded by drainage and subsequent land use.
However, beneficial effects of functioning peatlands, most of all carbon storage, have long
been recognized but remain difficult to recover. Fragmentation and a surrounding of
intensively used agricultural catchments with excess nutrients in air and waters further affects
the recovery of sites.
Under such conditions, highly competitive species such as Juncus effusus colonize
restored peatlands instead of peat forming Sphagnum. While the specific stoichiometry and
chemical composition makes Sphagnum litter recalcitrant in decomposition and hence,
effective in carbon sequestration, we know little about dynamics involving Juncus,
although this species provides organic matter in high quantity and of rather labile
quality.
To better understand decomposition in context of litter quality and nutrient availability,
we incubated different peat types for 70 days; I) recent, II) weakly degraded fossil,
and III) earthyfied nutrient rich fossil peat, amended with two 13C pulse-labelled
Juncus litter types (excessively fertilized ”F”, and nutrient poor “NF” plants grown
for three years watered with MilliQ only), respectively. We determined anaerobic
decomposition rates, compared potential rates extrapolated from pure materials with
measured rates of the mixtures, and tracked the 13C in the solid, liquid, and gaseous
phase. To characterize the biogeochemical conditions, inorganic and organic electron
acceptors, hydrogen and organic acids, and total enzyme activity were monitored. For
characterization of dissolved organic matter we used UV-Vis and fluorescence spectroscopy
(parallel factor analysis), and for solid organic matter elemental analysis and FTIR
spectroscopy.
There were two main structural differences between litter types: “F” litter and its
leachates contained more proteinaceous components, the C/N ratio was 20 in contrast to 60 of
the “NF” litter. However, humic components and aromaticity were higher in “F” litter.
Generally, decomposition rates of litter were 5-30 times higher than of peat. Rates in
batches amended with “F” were lower compared to “NF” for the respective peat,
opposing typically reported observations. Nevertheless, the 13C label suggested that in
case of peat I and III preferably the litter was decomposed, decomposition of peat
II was apparently stimulated when “NF” was added, albeit this litter was poor in
nutrients. Multiple linear regression identified specific absorption at 254 nm (SUVA), a
measure of aromaticity representative for an array of inter-correlating spectroscopic
features, and enzyme activity as most important predictors for C-mineralization rates.
These two parameters explained 88% of the variance. Although enzyme activity
and SUVA did not correlate in the mixed assays, this was the case for the pure
materials (R2=0.95), suggesting an inhibitory effect of aromatic components on enzyme
activity.
This study confirms that generally litter quality is a major control for mineralization and
hence, carbon storage in peatlands. Interestingly, in the case of Juncus effusus, high nutrient
availability in peat and litter did not lead to enhanced degradation of the litter itself or
priming of decomposition of the surrounding peat. Furthermore, the results underline the
substantial contribution of Juncus biomass to C-cycling and potentially high C-emissions in
restored peatlands. |
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