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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,

    Corresponding author
    1. Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden
    • Department of Earth Sciences, Air Water and Landscape Sciences, Uppsala University, Uppsala, Sweden
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  • Thomas Grabs,

    1. Department of Earth Sciences, Air Water and Landscape Sciences, Uppsala University, Uppsala, Sweden
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  • Ishi Buffam,

    1. Department of Biological Sciences and Department of Geography, University of Cincinnati, Cincinnati, USA
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  • Hjalmar Laudon,

    1. Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden
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  • Anneli Ågren,

    1. Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden
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  • Mats G. Öquist,

    1. Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden
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  • Kevin Bishop

    1. Department of Earth Sciences, Air Water and Landscape Sciences, Uppsala University, Uppsala, Sweden
    2. Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden
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Correspondence: Marcus B. Wallin, tel. +46 18-4712529, fax +46 18 55 11 24, e-mail: marcus.wallin@geo.uu.se

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.

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