Total waterborne carbon export and DOC composition from ten nested subarctic peatland catchments—importance of peatland cover, groundwater influence, and inter-annual variability of precipitation patterns

摘要

Waterborne carbon (C) export from terrestrial ecosystems is a potentially important flux for the net catchment C balance andlinks the biogeochemical C cycling of terrestrial ecosystems to their downstream aquatic ecosystems. We have monitoredhydrology and stream chemistry over 3 years in ten nested catchments (0.6–15.1 km2) with variable peatland cover (0%–22%)and groundwater influence in subarctic Sweden. Total waterborne C export, including dissolved and particulate organic carbon(DOC and POC) and dissolved inorganic carbon (DIC), ranged between 2.8 and 7.3 gm–2 year–1, representing ~10%–30% ofcatchment net ecosystem exchange of CO2. Several characteristics of catchment waterborne C export were affected by interactingeffects of peatland cover and groundwater influence, including magnitude and timing, partitioning into DOC, POC, and DIC andchemical composition of the exported DOC. Waterborne C export was greater during the wetter years, equivalent to an averagechange in export of ~2 gm–2 year–1 per 100mm of precipitation. Wetter years led to a greater relative increase in DIC export thanDOC export due to an inferred relative shift in dominance from shallow organic flow pathways to groundwater sources. Indicesof DOC composition (SUVA254 and a250/a365) indicated that DOC aromaticity and average molecular weight increased withcatchment peatland cover and decreased with increased groundwater influence. Our results provide examples on how waterborneC export and DOC composition might be affected by climate change. Copyright © 2012 John Wiley & Sons, Ltd.