Resumo

HERNANDEZ-VALENCIA, Ismael  e  MONTSERRAT, Bautis. Changes in phosphorus content in the topsoil by the conversion of savanna to pine forest . Bioagro [online]. 2005, vol.17, n.2, pp.69-78. ISSN 1316-3361.

We assessed the changes in P fractions, acid phosphatase activity, and phosphate sorption by the establishment of a pine forest on an acidic, sandy savanna soil. After 24 years, it was found an increase in organic matter and its light fraction content in the topsoil, which in turn influenced the phosphate sorption capacity. Among the different chemical and microbiological P fractions, only the organic moderately labile pool (Po-NaOH) showed a small but significant increase and indicates that the establishment of the pine forest has had a low impact on the different P fractions. The bioavailable Pi/Po ratio showed a higher P deficiency for the pine forest and consequently a more rapid cycling to satisfy P requirements in this ecosystem. However, P deficiency did not correlate with phosphatase activity. This finding supports previous studies where it has been determined that phosphatase activity is a good indicator of potential mineralization, but not for real Po mineralization rates.

Palavras-chave : Pinus caribea; oxisol; P fractionaction; phosphatase activity; P sorption.