Effects of burning and grazing on carbon sequestration in a Pennine blanket bog, UK

Terrestrial ecosystems contain large amounts of carbon (C) and have the pot ential to significantly increase atmospheric carbon dioxide (CO2) concentra tions. Peatlands are particularly important for C storage, although little is known about the effects of anthropogenic activities on C balance in thes e ecosystems. Sheep-grazing and rotational burning are widely practised on blanket peat moorlands in the United Kingdom. The effects of these activiti es on C sequestration in peat has been investigated with a long-term random ized block experiment with treatments: (a) grazed 1 unburnt; (b) grazed 1 b urnt every ten years; (c) ungrazed 1 unburnt. C accumulation under these tr eatments was compared by identifying a chronologically synchronous horizon within the peat common to all treatment plots. This fixed point was defined by the 'take-off' in concentration of spheroidal carbonaceous particles an d was supported by the record of charcoal fragments. There was no significa nt difference in recent C accumulation rates between lightly grazed and ung razed plots. In contrast, after 30 years there was significantly less C sto red in the blanket peat in plots which had been burned every ten years. The results indicate that light sheep-grazing at this site did not affect rate s of C accumulation in blanket peat, but decadal burning of moorland reduce d C sequestration.