The role of hillslope position in controlling carbon flux from peatlands

Peatlands are important terrestrial carbon stores, both in the United Kingdom and globally. The cool and wet climate of the UK allows blanket bog peatlands to form in upland regions, with peat deposits covering the landscape across entire hillslopes. Blanket bogs are important sinks and sources of CO2 and dissolved organic carbon (DOC). Many factors affect the carbon cycle of peatlands, including climate, hydrology, vegetation, land management and topography. Although hillslope position can influence the hydrology of peatlands, the effect it has on the production and transport of different carbon species is poorly understood. This thesis investigates the impact hillslope position has upon the hydrology and carbon release pathways of blanket bogs in upland regions. Hydrology, CO2 fluxes and DOC concentrations were studied at two hillslopes in the Peak District, Derbyshire, across four hillslope positions: top-slope, upper mid-slope, lower mid-slope and bottom-slope. Results show that slope position was the dominant control affecting water table variation. Although slope position did influence variation in CO2 fluxes, its impact was small compared to other factors, including small-scale heterogeneity and microtopographic variation. Slope position was an important control influencing variation in DOC concentrations. Dissolved organic carbon concentrations decreased down-slope as high water tables and water movement flushed DOC from the peat subsurface. Model results indicate that slope position is an important factor that should be included in carbon budget models but further work is required to further improve understanding of hillslope processes.