The relative influence of land cover, hydrology, and in-stream processing on the composition of dissolved organic matter in boreal streams

Kothawala, Dolly N. and Ji, Xing and Laudon, Hjalmar and Ågren, Anneli M. and Futter, Martyn N. and Köhler, Stephan J. and Tranvik, Lars J. (2015) The relative influence of land cover, hydrology, and in-stream processing on the composition of dissolved organic matter in boreal streams. Journal of Geophysical Research: Biogeosciences. ISSN 2169-8961

[img] PDF
Kothawala et al. 2015.pdf

Download (2MB)
Official URL:


Low-order boreal streams are particularly sensitive interfaces where dissolved organic matter (DOM) is transported from soils to inland waters. Disentangling the relative influence of key environmental factors suspected to influence stream water DOM composition is highly relevant to predicting the reactivity and fate of terrestrial DOM entering inland waters. Here we examined changes to DOM composition using absorbance and fluorescence, from 17 boreal streams ranging from first to fourth orders, over 14 months, including the rarely studied winter season, and two snowmelt periods (n = 836). We also analyzed soil pore water samples from three forest soil lysimeters to a depth of 70 cm (n = 60). Of five identified fluorescing parallel factor analysis components, two (C4 and C5) expressed a clear mire wetland or forest signature, providing distinct molecular markers of dominant land cover. In fact, land cover alone explained 49% of the variability in DOM composition. In contrast, seasonal fluctuations in hydrology only contributed to minor shifts (8%) in the composition of stream water DOM, while in-stream transformations to DOM composition were undetectable. These findings suggest that low-order boreal streams act as a passive pipe, since in-stream processing of DOM is restricted by short water residence times (6 h to 2 days). In addition, we demonstrated the sensitivity of optical approaches to distinguish between key terrestrial sources of DOM in the boreal landscape. By distinguishing the proportional leverage of key environmental controls on headwater stream DOM composition, we are better equipped to predict where and when key DOM transformations occur in the aquatic conduit.

Item Type: Article
Language: English
Uncontrolled Keywords: dissolved organic matter; PARAFAC; boreal streams; land cover; hydrology; fluorescence; 0414 Biogeochemical cycles, processes, and modeling; 0428 Carbon cycling; 0497 Wetlands; 1615 Biogeochemical cycles, processes, and modeling
Future Forest Subject: Skogsbruk i klimatförändringens tid > Natur
Depositing User: Christer Enkvist
Date Deposited: 28 Feb 2017 14:26
Last Modified: 28 Feb 2017 14:26

Actions (login required)

View Item View Item