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Dissolved organic carbon characteristics in boreal streams in a forest-wetland gradient during the transition between winter and summer
Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
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2008 (English)In: Journal of Geophysical Research, Vol. 113, G03031- p.Article in journal (Refereed) Published
Abstract [en]

The character and quantity of dissolved organic carbon (DOC) were studied in nine small boreal streams and adjacent soils during two years, with focus on the spring snowmelt period. The streams cover a forest-wetland gradient, spanning from 0% to 69% wetland coverage. Lower values of the absorbance ratio measured at 254 nm and 365 nm (A254/A365), in both soil plots and streams, indicated that wetland-derived DOC had higher average molecular weight than forest DOC. Higher SUVA254 (DOC specific ultraviolet absorption at 254 nm) in wetland runoff indicated more aromatic DOC from wetlands than forests. During low flow, the stream DOC character was sensitive to the forest-wetland proportion of the catchment, and when wetland coverage exceeded 10%, the streams appeared to be dominated by wetland-derived DOC. During the spring snowmelt period, the character changed to lower molecular weight and more aliphatic DOC, particularly in streams with a high proportion of forest in the catchment. The forested soil solutions had higher A254/A365 in the surface horizons that were hydrologically activated during the high flow events, while wetland soil solution had relatively low A254/A365 at all depths. Consequently forest soils contributed more to stream DOC concentration during snowmelt that during winter low flow.

Place, publisher, year, edition, pages
2008. Vol. 113, G03031- p.
Identifiers
URN: urn:nbn:se:umu:diva-11415DOI: doi:10.1029/2007JG000674OAI: oai:DiVA.org:umu-11415DiVA: diva2:151086
Available from: 2009-01-08 Created: 2009-01-08 Last updated: 2011-01-10Bibliographically approved
In thesis
1. Seasonal variation and landscape regulation of dissolved organic carbon concentrations and character in Swedish boreal streams
Open this publication in new window or tab >>Seasonal variation and landscape regulation of dissolved organic carbon concentrations and character in Swedish boreal streams
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The seasonal variation and landscape regulation of dissolved organic carbon (DOC) concentrations in streams have been studied in two watersheds in the boreal zone. The seasonal variation was found to be highly correlated to variations in runoff. An increase in runoff was always accompanied with an increase in DOC concentration. However, there were indications that the TOC concentration was restricted by the soil TOC pool during snowmelt.

The main factors affecting DOC exports varied between seasons. During winter baseflow the spatial variation in DOC exports was strongly influenced by wetland coverage, during snowmelt the exports were correlated to factors describing the size and location of the catchment, and during the snow-free season they were heavily affected by the proportions of wetlands and forests in the catchments. Small headwaters had the highest terrestrial DOC export, per unit area.

The properties of the DOC changed during spring flood, towards lower molecular weight and more aliphatic compounds. These changes affected the bioavailability of the DOC, which increased during spring flood. There were also differences in the DOC properties between wetlands and forest soils; the forested soils yielded DOC with lower molecular weight (measured as 254 nm/365 nm light absorbance ratios), largely from superficial layers that were activated during high flow events, while wetland soils generally provided a more constant carbon source with higher molecular weight. The majority of the DOC was exported by wetlands, but most of the short-term bioavailable DOC (BP7) was derived from the forests, during the spring flood period, indicating that bacterial production in streams and lakes is likely to be almost entirely based on DOC exported from forested areas during, and some time after, the spring flood event.

Place, publisher, year, edition, pages
Umeå: Ekologi, miljö och geovetenskap, 2007. 35 p.
Keyword
DOC, temporal variation, spatial variation, seasonal variation, forested catchment, wetland catchment, catchment characteristics, DOC characteristics, absorbance-ratio, bioavailability.
National Category
Physical Geography
Identifiers
urn:nbn:se:umu:diva-1374 (URN)978-91-7264-372-7 (ISBN)
Public defence
2007-10-19, KB3A9, KBC, Umeå universitet, Umeå, 09:00 (English)
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Supervisors
Available from: 2007-09-28 Created: 2007-09-28 Last updated: 2010-01-08Bibliographically approved

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Berggren, MartinJansson, MatsLaudon, Hjalmar

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