Nutrient dynamics of soil derived from different parent material on Barro Colorado Island, Panama

I compared the concentrations of N, P, and S in both litter and mineral soil (0-15 cm depth) from three old-growth, tropical moist Forests on Barro Colorado Island (BCI), Panama. Each site was on a different substrate (i.e. parent material), hut otherwise had similar climate, vegetation, and topography. There were no site differences in concentrations of N and S for either litter or soil. Concentrations of litter P and soil-extractable P were greater for the andesite (igneous rock) site than for two sites On different sedimentary rocks; however, concentrations of several other litter and soil P fractions did not differ among sites. Patterns in soil P fractions suggested advanced soil development to the point that parent material has little control of P dynamics. Litter samples from each site, leached in the laboratory, released similar amounts of N, P, and S to the soil, indicating no differences in rates of turnover in the litter and in fluxes from litter into the mineral soil among sites. I expected more site differences in soil nutrient dynamics given vastly different parent materials and soil types (i.e., Oxisol vs. Alfisol) and very shallow soil on BCT chat brings the parent material close to the plant root zone. Erosion and soil mixing may explain the uniformity in soil nutrient dynamics across the sites.