Study of current dynamics of soils from a podzol-oxisol sequence in Tahiti (French polynesia) using the test-mineral technique

Abstract The current soil dynamics of a podzol-oxisol climosequence located in Tahiti on basaltic and pyroclastic parent rocks has been investigated using the “test-mineral” technique. The test-mineral, a vermiculite with a high exchange capacity (161 meq/100 g) was placed in recoverable bags in the A and B horizons of three members of the sequence, for periods of 1 to 3.5 years. Changes in the chemistry and mineralogy, enabling complexing acid environments to be distinguished from non-complexing, were determined following the in situ reaction with natural soil leachates. A set of leachates from the same horizons were collected and chemically analysed at the end of 3.5 years. The results indicate that the current acid environment is only weakly complexing. This suggests that the podzolisation processes which led to the development of a unique A2 horizon containing gibbsite, anatase and rutile, and a placic horizon, in the upper podzol member of the sequence, is no longer operating.