Towards sound comparisons of soil carbon stocks: A proposal based on the cumulative coordinates approach
Abstract The study of changes in soil organic carbon (SOC) stocks as a result of land use or climate change requires sound criteria to compare SOC stocks in different plots. Just comparing SOC stored down to a standard depth (often, 30 cm) is prone to errors, owing to the changes in soil bulk density due to shifts in SOC content or the soil compaction due to heavy machinery. To solve this problem several approaches have been suggested. Jenkinson proposed in 1971 the concept of ‘equivalent soil depth’, the depth to which a soil should be sampled to reach a certain amount of fine mineral earth. Here we present a procedure which combines that concept with the modern cumulative coordinates approach (CCA). Our method involves sampling soils down to a given depth (30 cm) with a volumetric core sampler which maintains the profile structure, and divide the obtained core in depth layers (0–5, 5–15 and 15–30 cm). Each layer is studied separately for its stone and gravel content, fine earth (