Forested peatland margins as biogeochemical control points of dissolved organic carbon export

Peatlands store large carbon reservoirs, but the landscape controls on their lateral carbon losses remain insufficiently resolved. We investigated dissolved organic carbon (DOC) concentrations and export along a bog–swamp forest–Klyuch River continuum within the Great Vasyugan Mire, Western Siberia. Peat-profile characterization, pore-water chemistry and hydrometeorological monitoring were combined to assess spatial and seasonal DOC patterns. Swamp-forest waters at the thicker-peat site contained more DOC than waters from the open sedge–Sphagnum bog and the shallow-peat forest. The contrast between the two forested sites indicates that forest cover alone is insufficient to explain DOC enrichment. Pore-water DOC varied with peat decomposition and water-table conditions, while bulk peat TOC was a weaker predictor. Riverine DOC concentrations were higher in the forest-draining tributaries than in the main channel. Concentration and export maxima were seasonally separated: DOC concentrations were highest during the warm season, whereas the largest export occurred during spring high flow. These findings identify hydrologically connected swamp-forest margins as important DOC-rich source areas within the studied catchment. They also show why peatland carbon assessments should distinguish carbon availability in pore waters from the hydrological timing of export. Warming, changing precipitation and vegetation shifts may alter these source–transport linkages, but the direction and magnitude of future lateral carbon loss will depend on runoff and retention as well as DOC production.