The influence of soil age and regional climate on clay mineralogy and cation exchange capacity of moist tropical soils: A case study from Late Quaternary chronosequences in Costa Rica

The age-related evolution of tropical soils appears to be a predictable sequence in lowland tropical landscapes where periodic tectonism, erosion or volcanism produces unweathered parent material at the land surface. Empirical data from this project enables the extrapolation of simple equations applicable to tropical volcanic arc landscapes where presence of uplifted marine terrace soils facilitates determination of soil age. The two variables controlling soil composition can be combined into an effective age (ageeff) that takes into account soil age and weathering intensity (factoring in MAP and wet-dry months from climate data), and equations are of the form, e.g. ECEC = − 18.1 ∗ ln(ageeff) + 77, with R2 values of 0.75 to 0.87. Greatest scatter occurs in the youngest soils. Given the apparent prevalence of this sequence and the systematic nature of its reaction progression, these results could be useful for modeling tropical soils.