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

Winterdahl, Mattias and Wallin, Marcus B. and Karlsen, Reinert Huseby and Laudon, Hjalmar and Öquist, Mats and Lyon, Steve W. (2016) Decoupling of carbon dioxide and dissolved organic carbon in boreal headwater streams. Journal of Geophysical Research: Biogeosciences, 121 (10). pp. 2630-2651. ISSN 2169-8961

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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 (<24 h). 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 = 17 km). 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.

Item Type: Article
Language: English
Uncontrolled Keywords: DOC, 0414 Biogeochemical cycles, processes, and modeling , 0428 Carbon cycling , 1804 Catchment , 1830 Groundwater/surface water interaction , 1856 River channels
Future Forest Subject: Skogsbruk i klimatförändringens tid > Natur
Depositing User: Christer Enkvist
Date Deposited: 03 Apr 2017 09:48
Last Modified: 03 Apr 2017 09:48

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