Theoretical analyses of carbon and nutrient dynamics in soil profiles

The study of C, N, P, and S profiles in soils can tell us about the rates and pathways within and interactions between the cycles of the four elements in the whole ecosystem. We now add a spatial dimension to the continuous quality theory such that it can describe the distribution of the four elements along the vertical direction in the soil. This extension requires the introduction of a new function describing the velocity with which the organic matter moves along the soil profile. The theory is used to calculate properties of storage and mineralisation rates of C, N, P and S in soil profiles; for example, how is the position of the maximum of the density profiles determined by the rate of decomposition relative to the rate of transport. Predictions of the theory agree well with empirical information from agricultural and forest soils. A refined analysis would require better knowledge of the velocity of transport and its explicit dependence on quality and abiotic factors.