A Look at Amazon Basin Seasonal Dynamics with the Biophysical ...

LATERAL VARIATIONS IN THE CHEMICAL PROPERTIES OF THE TERRAFIRM SOILS, ESECAFLOR EXPERIMENT (CAXIUANÃ, PARÁ STATE)Simone Baía Pereira (MPEG/LBA)Maria de Lourdes Ruivo (MPEG/LBA)The relationships between water exclusion, properties of soil and forest cycle areinvestigated by “The Impact of drought on water and carbon dioxide fluxes from brazilianrain forest – ESECAFLOR project, located in Ferreira Penna Scientific Station (Caxiuanã,Pará). Treatment (B) and control (A) plots were established in the forest. Each plot had fourtrenches (A1, A2, A3, A4 and B1, B2, B3, B4). In A and B plots there are not lateralappreciable changes. In this study were evaluate the seasonal variability from the selectedchemical properties in the surface soils (0-25 cm) the samples were collected the early rainyseason (January /2000) and dry season (Jane/2001). The organic carbon content (plot A)was significantly higher in the rain season, increased diagonally in the both plots. In the dryseason, the organic carbon content is smaller compared with rain season. The observationsin dry period indicate small increase in the pH values. The increase tendency ofexchangeable Ca 2+ and Mg 2+ and pH is contrary between the A and B plots. In dry season,A1 trench showed the low valor of organic carbon (7.05 g/Kg), exchangeables Ca 2+ (0.112cmolc/dm 3 ) and Mg 2+ (0.112 cmolc/dm 3 ) and high value pH (4.7); and B3 trench exhibitedorganic carbon content near to minimal value (5.04 g/Kg) and pH is maximum (4.4).Clearly indicate an association with minimal percentage of humid, 18.6 and 14.7%, to Aand B plots, respectively. These observations, probably, indicate the A1 and B3 trencheshas major altitude, in relation to other trenches, cause higher weathering and aeration.Consequently, fast decomposition of organic matter. The increase pH may be due to theretreat weak acids of the environment, and decrease of the exchangeables cations.