Nitrogen, Phosphorus, and Sulfur Properties of Some Forest Soils on Barro Colorado Island, Panama

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Abstract
Eight surface soils from lowland tropical moist forest on Barro Colorado Island, Panama, were evaluated for: (1) NH4+-N, NO3--N, PO43--P, and SO42--S concentrations in 10-mM CaCl2 extractions; (2) N, P, and S mineralization potentials in laboratory incubations; and (3) total N, P, and S concentrations. Concentrations of NH4+-N, NO3--N, and PO43--P prior to incubation were similar among the soils despite significant differences in total C, N, and P concentrations. Initial concentrations of SO42--S generally were greater in basalt-derived soils than in sediment-derived soils, although a similar pattern in total S concentrations among these site was not observed. The new mineralization potentials of the eight soil types had three characteristics in common: (1) most of the mineralized N was nitrified, and NO3--N accumulated at an approximately linear rate over a 32-day incubation period; (2) PO43--P decreased between days 0 and 16, then increased more than ten times between days 16 and 32; and (3) SO42--S did not change over time. The striking consistency in the patterns of net mineralization among the eight soils was unexpected because of differences in the total element contents of the soils and in the parent materials, vegetation on the site, and history of disturbance to the vegetation.