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Forskningsartikel2016Vetenskapligt granskadÖppen tillgång

Decoupling of carbon dioxide and dissolved organic carbon in boreal headwater streams

Winterdahl, Mattias; Wallin, Marcus B.; Karlsen, Reinert Huseby; Laudon, Hjalmar; Oquist, Mats; Lyon, Steve W.


Streams and rivers emit large quantities of carbon dioxide (CO2) to the atmosphere. The sources of this CO2 are in-stream mineralization of organic carbon (OC) and CO2 input via groundwater inflow, but their relative importance is largely unknown. In this study, we quantified the role of in-stream OC mineralization as a source of CO2 in a number of nested boreal headwater streams. The results showed that mineralization of stream OC contributed 3% of CO2 supersaturation at time scales comparable to the estimated water travel times in the streams (<24h). Mass balances showed that downstream losses of OC were 3% in low-order streams, whereas up to 16% of the OC was lost in the largest (fourth order) streams. In contrast, 85% of the CO2 was lost along the stream network (longest total stream length=17km). Under the assumption that in-stream OC mineralization was the main source of stream CO2, higher rates of OC mineralization (6% of OC) than those reported across the literature (0.7% of OC) would be required to sustain observed CO2 supersaturation. Further, model results indicated that groundwater inflows were sufficient to sustain observed stream CO2 concentrations. We hence conclude that in-stream OC mineralization was a minor source of CO2 in these boreal headwater systems and that the main source of stream CO2 was inflowing groundwater transporting CO2 originating from soil respiration.


DOC; CO2; mass balance; water-atmosphere exchange; Riparian flow-concentration Integration Model

Publicerad i

Journal of Geophysical Research: Biogeosciences
2016, Volym: 121, nummer: 10, sidor: 2630-2651