Spatial Variability of Terrestrial Carbon Inputs from the Catchment to Reach Scale in SubArctic, Sweden

As the Arctic continues to warm, shifting hydrological flow paths due to permafrost thaw can move highly biodegradable, terrestrial-derived carbon (C) into streams, potentially increasing carbon dioxide (CO₂) and methane (CH₄) emissions. Most studies characterize these C fluxes from a single point within a catchment, typically at large river outlets. However, different land cover types across the landscape can serve as “control points”, disproportionately contributing dissolved organic carbon (DOC), CO₂, and CH₄ to streams. To investigate the spatial variability of aquatic C emissions and landscape connectivity across a subcatchment, we sampled riparian porewater and stream water. Our study subcatchment is 15 km2 and includes the permafrost peatland Stordalen Mire in northern Sweden (68°21′ N 18°49′ E). There are four stream branches with landscape transitions from alpine tundra to birch forest to a discontinuous permafrost peatland. We characterized groundwater inputs, dissolved C, CH₄ and CO₂ fluxes along each stream branch within each land cover type and more frequently in the permafrost peatland. Both DOC and DIC concentrations varied throughout the catchment and were highest in the stream reaches that pass through the peatland. Total dissolved nitrogen and CH₄ concentrations did not vary significantly throughout the catchment, potentially indicating shorter resident times.  δ13C-CO₂ signatures indicate microbial sources in lakes and in stream reaches that drain the peatland. Ebullitive CH₄ was highest at the stream outlet and varied across the peatland reach. Further understanding of the controls of this variability are crucial for understanding watershed-scale lateral C flux as well as C transformation as these ecosystems warm.

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Primary Presenter: Cheristy Jones, University of New Hampshire (cheristy.jones@unh.edu)

Authors:

Cheristy Jones, University of New Hampshire  (cheristy.jones@unh.edu)

McKenzie Kuhn, University of British Columbia  (mckenzie.kuhn@ubc.ca)

Lyreshka Castro Morales, University of British Columbia  (lyreshka@gmail.com)

Carolina Olid, University of Barcelona  (carolina.olid@ub.edu)

Apryl Perry, University of New Hampshire  (apryl.perry@unh.edu)

Brayden King, University of Miami  (kingbenny787@gmail.com)

Jeff Chanton, Florida State University  (jchanton@fsu.edu)

Jan Karlsson, Umeå University  (jan.p.karlsson@umu.se)

Ruth Varner, University of New Hampshire  (ruth.varner@unh.edu)