Refinement of the carbon to loss on ignition relationship in forest soils

Loss on ignition (LOI) is a common method for determining organic matter in soils. Mineral soil organic carbon content has been shown to be approximately 50%–58% of the organic matter in many soils, but the carbon fraction of LOI can actually be much lower—particularly in Spodosols. We leveraged data available in the International Soil Carbon and National Ecological Observatory Networks to evaluate departures from the common 50% rule. We offer empirical equations that more accurately predict C:LOI with depth and genetic horizon in Spodosols. These equations enable more accurate soil C stock appraisals than using assumed C:LOI ratios.