The archetypal tropical soil is highly leached, with low Ca and high Al. However, 65% of soils from moist-to-wet tropical environments do not fit this description, particularly those in tectonically active environments. Cation exchange capacity (CEC) of soils plays an integral role in nutrient cycling in terrestrial ecosystems. The goal of this study is to investigate variations in CEC as a function of soil age and mean annual precipitation (MAP) along the Pacific coast of Costa Rica. It is expected that older, more weathered soils will have lower CEC relative to younger soils. Higher MAP is expected to increase rate of leaching, causing a more rapid decrease in CEC as a function of age. Preliminary results demonstrate that CEC of smectite rich, ≤10 ka, soils range from 45-90 cmolc/kg, and at the other extreme, CEC of kaolinite dominated 120 ka soils ranges from 1-15 cmolc/kg.
