Gully hotspot contribution to landscape methane (CH4) and carbon dioxide (CO2) fluxes in a northern peatland.

Peatlands are long term carbon catchments that sink atmospheric carbon dioxide (CO(2)) and source methane (CH(4)). In the uplands of the United Kingdom ombrotrophic blanket peatlands commonly exist within Calluna vulgaris (L.) dominated moorland ecosystems. These landscapes contain a range of topographical features that influence local hydrology, climate and plant community composition. In this study we examined the variation in ecosystem CO(2) respiration and net CH(4) fluxes from typical plant-soil systems in dendritic drainage gullies and adjacent blanket peat during the growing season. Typically, Eriophorum spp., Sphagnum spp. and mixed grasses occupied gullies while C. vulgaris dominated in adjacent blanket peat. Gross CO(2) respiration was highest in the areas of Eriophorum spp. (650+/-140 mg CO(2) m(-2) h(-1)) compared to those with Sphagnum spp. (338+/-49 mg CO(2) m(-2) h(-1)), mixed grasses (342+/-91 mg CO(2) m(-2) h(-1)) and C. vulgaris (174+/-63 mg CO(2) m(-2) h(-1)). Measurements of the net CH(4) flux showed higher fluxes from the Eriophorum spp (2.2+/-0.6 mg CH(4) m(-2) h(-1)) locations compared to the Sphagnum spp. (0.6+/-0.4 mg CH(4) m(-2) h(-1)), mixed grasses (0.1+/-0.1 mg CH(4) m(-2) h(-1)) and a negligible flux detected from C. vulgaris (0.0+/-0.0 mg CH(4) m(-2) h(-1)) locations. A GIS approach was applied to calculate the contribution of gullies to landscape scale greenhouse gas fluxes. Findings from the Moor House National Nature Reserve in the UK showed that although gullies occupied only 9.3% of the total land surface, gullies accounted for 95.8% and 21.6% of the peatland net CH(4) and CO(2) respiratory fluxes, respectively. The implication of these findings is that the relative contribution of characteristic gully systems need to be considered in estimates of landscape scale peatland greenhouse gas fluxes.