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

CHEMICAL COMPOSITION OF THE SOILWATER IN THE SUBSURFACEAFTER THE SLASHING AND BURNING OF TWO “TERRA FIRME” FORESTPARCELS IN NORTHERN MATO GROSSO.Ralf Gielow 1 , Maria Cristina Forti 1 , João Andrade de Carvalho Jr 2 , Carlos Alberto GurgelVeras 3 , Ernesto Alvarado 4 , David Victor Sandberg 5 , José Carlos dos Santos 61. LMO/CPTEC/INPE, C. P. 515, São José dos Campos, SP, CEP 12201-970ralf@cptec.inpe.br2. FEG/UNESP, Guaratinguetá, SP3. ENM/UnB, Brasília, DF4. U W, Seattle, WA5. USDA FS, Corvallis, OR6. LCP/INPE, Cachoeira Paulista, SPABSTRACTChanges in the chemical composition, with depth and time, of the soil water solution thatresults from rainfall and that percolates through the unsaturated zone, are studied after theslashing and burning of two “Terra Firme” Amazonian forest parcels located (9 o 57'42.20"S,56 o 20'52.05"W) near Alta Floresta, MT. The samples were collected with zero tensionlisymeters installed in the following parcels: (i) pristine forest, (ii) forest with the litteraccidentally burned, (iii) and (iv) slashed and burned forest, in 1999 and 2001, respectively.The concentrations of Na + , K + , Mg 2+ , Ca 2+ , NH 4 + , Cl - , NO 3 - , SO 4 2- , Fe 2+ , Mn 2+ , Cu 2+ , Zn 2+and Al 3+ in the soil solution were determined. The major cations and anions presented aconcentration decrease with time, after initial peaks caused by the burning, while for mostmetals a mobilization was observed. Also, unbalances which decrease with time wereevidenced by the electronegativities determined. The pulses introduced in the soil solutioncomposition lasted about two months for each major ion, and react with the soil system.