Soil pH, organic matter, and concentrations of extractable-P, exchangeable K, Ca, Mg and Al were measured in selectively logged plots of upland rain forest, 80 km north of Manaus. Soil type corresponds to an acid and very clayey Oxisol, (ca. 80 % of clay). Two control plots of intact forest and two plots submitted to selective logging were studied in 1987 and 1993. Results confirmed high soil acidity, and showed highest concentrations of extractable-P, and exchangeable-K, Ca, Mg and Al in the wet season. Both control and logged plots, showed the following ranking of concentrations for soil pit analyses: Al > Ca > Κ > Mg, in the wet season, and Al > Κ > Mg > Ca in the dry season. There are evidences that the timber residues left from selective logging rises soil nutrient values through decay, especially during the wet season.
Amazonia; soil nutrients; upland rain forest; selective logging