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| Titel |
Landscape heterogeneity drives contrasting concentration–discharge relationships in shale headwater catchments |
| VerfasserIn |
E. M. Herndon, A. L. Dere, P. L. Sullivan, D. Norris, B. Reynolds, S. L. Brantley |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 19, no. 8 ; Nr. 19, no. 8 (2015-08-03), S.3333-3347 |
| Datensatznummer |
250120775
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| Publikation (Nr.) |
 copernicus.org/hess-19-3333-2015.pdf |
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| Zusammenfassung |
| Solute concentrations in stream water vary with discharge in patterns that
record complex feedbacks between hydrologic and biogeochemical processes. In
a comparison of three shale-underlain headwater catchments located in
Pennsylvania, USA (the forested Shale Hills Critical Zone Observatory), and
Wales, UK (the peatland-dominated Upper Hafren and forest-dominated Upper
Hore catchments in the Plynlimon forest), dissimilar concentration–discharge (C–Q) behaviors
are best explained by contrasting landscape distributions of soil solution
chemistry – especially dissolved organic carbon (DOC) – that have been
established by patterns of vegetation and soil organic matter (SOM).
Specifically, elements that are concentrated in organic-rich soils due to
biotic cycling (Mn, Ca, K) or that form strong complexes with DOC (Fe, Al)
are spatially heterogeneous in pore waters because organic matter is
heterogeneously distributed across the catchments. These solutes exhibit
non-chemostatic behavior in the streams, and solute concentrations either
decrease (Shale Hills) or increase (Plynlimon) with increasing discharge. In
contrast, solutes that are concentrated in soil minerals and form only weak
complexes with DOC (Na, Mg, Si) are spatially homogeneous in pore waters
across each catchment. These solutes are chemostatic in that their stream
concentrations vary little with stream discharge, likely because these
solutes are released quickly from exchange sites in the soils during
rainfall events. Furthermore, concentration–discharge relationships of
non-chemostatic solutes changed following tree harvest in the Upper Hore catchment in Plynlimon, while no changes were observed for chemostatic
solutes, underscoring the role of vegetation in regulating the
concentrations of certain elements in the stream. These results indicate
that differences in the hydrologic connectivity of organic-rich soils to the
stream drive differences in concentration behavior between catchments. As
such, in catchments where SOM is dominantly in lowlands (e.g., Shale Hills),
we infer that non-chemostatic elements associated with organic matter are
released to the stream early during rainfall events, whereas in catchments
where SOM is dominantly in uplands (e.g., Plynlimon), these non-chemostatic
elements are released later during rainfall events. The distribution of SOM
across the landscape is thus a key component for predictive models of solute
transport in headwater catchments. |
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