Emission of highly 13C-depleted methane from an upland blanket mire

Rates and delta C-13 values of CH4 flux are reported from an upland blanket mire (Blaen Fign) situated in Wales UK. The delta C-13 values of CH4 flux were similar from Sphagnum and vascular flora dominated areas despite flux rates being an order of magnitude greater from the latter. Methane flux was C-13-depleted relative to belowground CH4, indicating that transport occurred predominately via passive diffusion through vascular flora and that pore water diffusion and ebullition contributed little to CH4 flux. The strong influence of vascular flora abundance on CH4 flux strength suggests that any factors altering vegetation assemblages in blanket mires will likely impact CH4 emission rates. Methane flux from Blaen Fign was highly C-13-depleted compared to emissions from minerotrophic wetlands, suggesting that delta C-13 values may be useful for tracing CH4 flux from blanket mires and other types of ombrogenous peatlands to the global CH4 budget.