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| Titel |
Sources and fate of terrestrial dissolved organic carbon in lakes of a Boreal Plains region recently affected by wildfire |
| VerfasserIn |
D. Olefeldt, K. J. Devito, M. R. Turetsky |
| 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 ; 10, no. 10 ; Nr. 10, no. 10 (2013-10-02), S.6247-6265 |
| Datensatznummer |
250085348
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| Publikation (Nr.) |
 copernicus.org/bg-10-6247-2013.pdf |
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| Zusammenfassung |
| Downstream mineralization and sedimentation of terrestrial dissolved organic
carbon (DOC) render lakes important for landscape carbon cycling in the
boreal region. The chemical composition of terrestrial DOC, the downstream
delivery of terrestrial DOC and its processing within aquatic ecosystem may
all be influenced by climate change, including increased occurrence of
wildfire. Here, we assessed composition and lability (during both dark- and
UV incubations) of DOC from peatland groundwater and mineral soil groundwater,
and from shallow lakes within a peatland-rich region on the Boreal Plains of western Canada that was recently affected by wildfire. Wildfire was found to increase aromaticity of DOC in
peat pore water above the water table, but had no effect on the
concentrations or composition of peatland groundwater DOC or mineral soil DOC. Using a mixing model we estimated that on
average 98 and 78% of terrestrial DOC inputs to the lakes in fine- and
coarse-textured settings, respectively, originated from peatland groundwater
sources. Accordingly, lake DOC composition reflected primarily a mixing of
peatland and mineral soil groundwater sources, with no detectable influence
of the recent wildfire. Lake and peatland DOC had low biodegradability,
lower than that of mineral soil DOC. However, both mineralization and
sedimentation of peatland DOC increased substantially during UV incubations
through selective removal of aromatic humic and fulvic acids. Similar shifts
in DOC composition as observed during the UV incubations were also observed
across lakes with longer water residence times. The mixing model estimated
that on average 54% (95% confidence interval: 36–64%) of
terrestrial DOC had been removed in lakes as a result of mineralization and
sedimentation. Meanwhile, the reduction in absorbance at 254 nm was 71% (58–76%), which suggests selective removal of aromatic DOC. Hence, incubation
results, patterns of DOC composition among lakes and mixing model results
were consistent with significant within-lake removal of terrestrial DOC
through UV-mediated processes. Selective removal of highly aromatic DOC
through UV-mediated processes implies that organic sources that are
considered stabile in terrestrial ecosystems can be readily mineralized once
entering aquatic ecosystems. Together, our results suggest that regional
characteristics (climate, surface geology and lake morphometry) can prevent
wildfire from causing pulse perturbations to the linkages between
terrestrial and aquatic C cycling and also regulate the processes that
dominate within-lake removal of terrestrial DOC. |
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