Modelling soil organic carbon distribution in blanket peatlands at a landscape scale

Blanket peat and other moorland soils store the largest proportion of the soil organic carbon resource (SOC) in the United Kingdom. However, current understanding of the quantity and distribution of upland SOC is limited and approaches are needed to quantify carbon storage over large areas, whilst adequately representing spatial variability at a smaller scale. This article presents a methodology for quantifying and mapping SOC distribution at a landscape scale in blanket peatlands on Dartmoor, South West England. Using stratified sampling, twenty-nine cores were taken from a range of depths within each of the soil types found in the study area. Depth was strongly correlated with bulk density (r2 = 0.70, P < 0.001) and loss on ignition (r2 = 0.51, P < 0.001) for blanket peat, with weaker or non-existent relationships in other soil types. These regression relationships were used with peat depth mapping, to model carbon distribution and quantity. The results estimate 9.7 ± 2.97 Mt of carbon is stored in Dartmoor's organic soils, and that blanket peat has a much higher carbon content per unit area than other organic soils. Sensitivity analysis revealed that bulk density and peat depth were equally influential in calculating carbon stocks, whilst variability in organic matter content was relatively unimportant. A comparison between the Dartmoor inventory and the national SOC inventory showed reasonable agreement for total C storage, but on an individual cell-by-cell basis disagreement between the inventories was often large. We conclude that when higher resolution SOC distribution is required (< 100 km2), such as for individual land holdings and management, the approach presented within this article provides a suitable carbon inventory