Carbon fluxes at an upland blanket bog in the north Pennines

Abstract

The peat soils found in blanket bogs are significant stores of carbon. The degree to which these ecosystems are currently functioning as sinks or sources of carbon is not clear. There is a paucity of measurements from suitable sites but the available evidence suggests that certain sites might be close to being carbon neutral or acting as a net source of carbon to the atmosphere. A complete understanding of the carbon budget of a landscape requires a
comprehensive assessment of the magnitude of the whole range of pathways by which carbon enters and leaves the system.

Measurements were made of all of the key gaseous carbon fluxes, including the net CO2 flux, the soil CO2 flux and emissions as methane. A flux partitioning model was utilised to separate the net CO2 flux into its component parts. Values for the fluvial carbon losses from the site were taken from the literature. The various CO2 fluxes were by far the largest terms in the complete carbon budget. Growing season measurements showed that methane emissions were a small component.

The key environmental variables that were driving the temporal variations in the fluxes were identified. In general soil temperature was important in explaining variations in ecosystem respiration, soil CO2 fluxes and the methane flux. The water table was usually high and fluctuations did not appear to affect carbon fluxes. There was evidence of increased soil CO2 fluxes as a response to low soil moisture levels during a summer dry
period.

A comprehensive carbon budget for the blanket bog at Moor House NNR showed the site to be a relatively large carbon sink, of an estimated 134.09 ± 32 g C m-2 yr-1.