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| Titel |
Multi-decadal water-table manipulation alters peatland hydraulic structure and moisture retention. |
| VerfasserIn |
Paul Moore, Paul Morris, James Waddington |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250107298
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| Publikation (Nr.) |
 EGU/EGU2015-6991.pdf |
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| Zusammenfassung |
| Peatlands are a globally important store of freshwater and soil carbon. However, there is a
concern that these water and carbon stores may be at risk due to climate change as vapour
pressure deficits, evapotranspiration and summer moisture deficits are expected to increase,
leading to greater water table (WT) drawdown in northern continental regions where
peatlands are prevalent. We argue that in order to evaluate the hydrological response (i.e.
changes in WT level, storage, surface moisture availability, and moss evaporation) of
peatlands under future climate change scenarios, the hydrophysical properties of peat
and disparities between microforms must be well understood. A peatland complex
disturbed by berm construction in the 1950’s was used to examine the long-term impact
of WT manipulation on peatland hydraulic properties and moisture retention at
three adjacent sites with increasing average depth to WT (WET, INTermediate
reference, and DRY). All three sites exhibited a strong depth dependence for hydraulic
conductivity, specific yield, and bulk density. Moreover, the effect of microform on
near-surface peat properties tended to be greater than the site effect. Bulk density
was found to explain a high amount of variance (r2 > 0.69) in moisture retention
across a range of pore water pressures (-15 to -500 cm H2O), where bulk density
tended to be higher in hollows. The estimated residual water content for surface
Sphagnum samples, while on average lower in hummocks (0.082 m3 m-3) versus
hollows (0.087 m3 m-3), increased from WET (0.058 m3 m-3) to INT (0.088 m3
m-3) to DRY (0.108 m3 m-3) which has important implications for moisture stress
under conditions of persistent WT drawdown. While we did not observe significant
differences between sites, we did observe a greater proportional coverage and greater
relative height of hummocks at the drier sites. Given the potential importance of
microtopographic succession for altering peatland hydraulic structure, our findings
point to the need for a better understanding of what controls the relative height and
proportional coverage of hummocks in relation to long-term disturbance-response
dynamics. While current peatland models can simulate bulk density that varies as
a result of changes in rates of production and decomposition for different plant
functional types and different microforms, the spatial component of microtopographic
succession is missing. We argue that the effects of microtopographic succession
on the spatial pattern of bulk density and associated hydrophysical properties are
important for capturing changes in hydraulic structure that result from disturbance. |
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