Abstract
The stability of northern peatland's carbon (C) store under changing climate is of major concern for the global C cycle. The aquatic export of C from boreal peatlands is recognized as both a critical pathway for the remobilization of peat C stocks as well as a major component of the net ecosystem C balance (NECB). Here, we present a full year characterization of radiocarbon content (14 C) of dissolved organic carbon (DOC), carbon dioxide (CO2 ), and methane (CH4 ) exported from a boreal peatland catchment coupled with 14 C characterization of the catchment's peat profile of the same C species. The age of aquatic C in runoff varied little throughout the year and appeared to be sustained by recently fixed C from the atmosphere (<60years), despite stream DOC, CO2 , and CH4 primarily being sourced from deep peat horizons (2-4m) near the mire's outlet. In fact, the 14 C content of DOC, CO2 , and CH4 across the entire peat profile was considerably enriched with postbomb C compared with the solid peat material. Overall, our results demonstrate little to no mobilization of ancient C stocks from this boreal peatland and a relatively large resilience of the source of aquatic C export to forecasted hydroclimatic changes.
Highlights
Northern peatlands have a central role in the global carbon (C) cycle, being the repository of a third of the global soil organic matter (~450 Pg; Gorham, 1991) and persistent sinks of contemporary atmospheric CO2 (Lund et al, 2010; Nilsson et al, 2008; Roulet et al, 2007)
The stability of northern peatland’s C stocks and their role in the C cycle under changing climate and increasing anthropogenic pressure is of major concern (Crowther et al, 2016; Wilson et al, 2016)
The aquatic export of C represents a major pathway for the mobilization of ancient peat C stocks, as well as being a critical component of the net ecosystem C balance (NECB; Billett, Garnett, & Dinsmore, 2015; Dinsmore et al, 2010; Nilsson et al, 2008)
Summary
Northern peatlands have a central role in the global carbon (C) cycle, being the repository of a third of the global soil organic matter (~450 Pg; Gorham, 1991) and persistent sinks of contemporary atmospheric CO2 (Lund et al, 2010; Nilsson et al, 2008; Roulet et al, 2007). The aquatic export of C represents a major pathway for the mobilization of ancient peat C stocks, as well as being a critical component of the net ecosystem C balance (NECB; Billett, Garnett, & Dinsmore, 2015; Dinsmore et al, 2010; Nilsson et al, 2008) It comprises organic C (TOC) and dissolved inorganic C (DIC), along with gaseous forms; mainly carbon dioxide (CO2), and methane (CH4), all of which can arise from the breakdown of either “old” peat material or more recently fixed carbon from the atmosphere (Billett et al, 2015; Leach, Larsson, Wallin, Nilsson, & Laudon, 2016; Wallin et al, 2013). This allowed us to identify the sources and main drivers of aquatic C export, information that is critical to determining the stability of the peatland C stock and its resilience to changes in climate and hydrology
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