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| Titel |
Winter climate affects long-term trends in stream water nitrate in acid-sensitive catchments in southern Norway |
| VerfasserIn |
H. A. Wit, A. Hindar, L. Hole |
| 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 ; 12, no. 2 ; Nr. 12, no. 2 (2008-03-05), S.393-403 |
| Datensatznummer |
250010563
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| Publikation (Nr.) |
 copernicus.org/hess-12-393-2008.pdf |
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| Zusammenfassung |
| Controls of stream water NO3 in mountainous and forested catchments are
not thoroughly understood. Long-term trends in stream water NO3 are
positive, neutral and negative, often apparently independent of trends in N
deposition. Here, time series of NO3 in four small acid-sensitive
catchments in southern Norway were analysed in order to identify likely
drivers of long-term changes in NO3. In two sites, stream water
NO3 export declined ca 50% over a period of 25 years while in the
other sites NO3 export increased with roughly 20%. Discharge and N
deposition alone were poor predictors of these trends. The most distinct
trends in NO3 were found in winter and spring. Empirical models
explained between 45% and 61% of the variation in weekly
concentrations of NO3, and described both upward and downward seasonal
trends tolerably well. Key explaining variables were snow depth, discharge,
temperature and N deposition. All catchments showed reductions in snow depth
and increases in winter discharge. In two inland catchments, located in
moderate N deposition areas, these climatic changes appeared to drive the
distinct decreases in winter and spring concentrations and fluxes of
NO3. In a coast-near mountainous catchment in a low N deposition area,
these climatic changes appeared to have the opposite effect, i.e. lead to
increases in especially winter NO3. This suggests that the effect of a
reduced snow pack may result in both decreased and increased catchment N
leaching depending on interactions with N deposition, soil temperature
regime and winter discharge. |
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