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Evasion of CO2 from streams – The dominant component of the carbon export through the aquatic conduit in a boreal landscape
Authors:Marcus B. Wallin  Thomas Grabs  Ishi Buffam  Hjalmar Laudon  Anneli Ågren  Mats G. Öquist  Kevin Bishop
Affiliation:1. Department of Earth Sciences, Air Water and Landscape Sciences, Uppsala University, , SE‐752 36 Uppsala, Sweden;2. Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, , SE‐750 07 Uppsala, Sweden;3. Department of Biological Sciences and Department of Geography, University of Cincinnati, , Cincinnati, OH 45221 USA;4. Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, , SE‐901 83 Ume?, Sweden
Abstract:Evasion of gaseous carbon (C) from streams is often poorly quantified in landscape C budgets. Even though the potential importance of the capillary network of streams as C conduits across the land–water–atmosphere interfaces is sometimes mentioned, low‐order streams are often left out of budget estimates due to being poorly characterized in terms of gas exchange and even areal surface coverage. We show that evasion of C is greater than all the total dissolved C (both organic and inorganic) exported downstream in the waters of a boreal landscape. In this study evasion of carbon dioxide (CO2) from running waters within a 67 km2 boreal catchment was studied. During a 4 year period (2006–2009) 13 streams were sampled on 104 different occasions for dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC). From a locally determined model of gas exchange properties, we estimated the daily CO2 evasion with a high‐resolution (5 × 5 m) grid‐based stream evasion model comprising the entire ~100 km stream network. Despite the low areal coverage of stream surface, the evasion of CO2 from the stream network constituted 53% (5.0 (±1.8) g C m?2 yr?1) of the entire stream C flux (9.6 (±2.4) g C m?2 yr?1) (lateral as DIC, DOC, and vertical as CO2). In addition, 72% of the total CO2 loss took place already in the first‐ and second‐order streams. This study demonstrates the importance of including CO2 evasion from low‐order boreal streams into landscape C budgets as it more than doubled the magnitude of the aquatic conduit for C from this landscape. Neglecting this term will consequently result in an overestimation of the terrestrial C sink strength in the boreal landscape.
Keywords:carbon budget  Greenhouse gases  headwaters  inland waters  water–  atmosphere exchange
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