Ten-year interannual and seasonal variability of stream carbon export from a boreal peatland in northern Sweden

Abstract:

High latitude peatlands constitute about 3% of the global land cover but store almost a third of the global soil carbon pool. The annual net ecosystem carbon balance at high latitude mires results from the balance between net ecosystem exchange, methane emission and stream discharge export. Understanding stream carbon export dynamics is needed to accurately predict how the carbon balance of peatlands will respond to climatic and environmental change. We use a ten year record (2004-2014) of streamflow and dissolved carbon (DOC, DIC, and CH4) measurements to assess interannual and seasonal variability in stream carbon export for a peatland catchment in northern Sweden. Mean annual total carbon export for the ten year period was 11.4 gC/m², but individual years ranged between 6.1 and 17.2 gC/m². DOC was the dominant form of carbon being exported, comprising 68% to 76% of total annual exports, and DIC contributed between 24% and 30%. CH4 made up less than 3% of total export. Stream carbon export and streamflow were highly synchronous. The majority of export (30% to 55% of annual totals) occurred during the spring snowmelt period. Exports during the summer and autumn were highly variable (1% to 45% and 9% to 53% of annual totals, respectively) and depended on the timing and magnitude of rain events. Winter periods were characterized by low streamflow conditions and associated low carbon export (0.6% to 10% of annual totals). These results highlight considerable interannual and seasonal variability of stream carbon export driven primarily by rain and snowmelt runoff events.