Influence of soil texture on the dynamics of dissolved organic carbon in soil solution of a primary forest in the Amazon ZF2, Manus
Vania
Neu, CENA - Centro de Energia Nuclear na Agricultura, vneu@esalq.usp.br
(Presenting)
Alex
Vladimir
Krusche, CENA - Centro de Energia Nuclear na Agricultura, alex@cena.usp.br
Joäo
Ferraz, INPA - Instituto Nacional de Pesquisas da Amazönia, jferraz@inpa.gov.br
The Amazon Rain Forest is characterized by several types of relief, vegetation, and soils. The biomass of this forest can be understood through its biochemical cycles. Within this context, carbon cycle is necessary for the maintenance of the Amazonian ecosystem. This study was conducted in a primary forest along a transect of gradient elevation at the ZF2 reserve INPA, Manaus. The main objective was the assessment of carbon dynamics, using soil solution, sampled weekly from March to August 2003. Tension lysimeters were installed at depth of 20 and 100 cm. Soil solution samples were preserved with HgCl2 and dissolved organic carbon (DOC) concentrations determined in a Shimadzu Total Organic Carbon Analyzer, model 5000A. Preliminary results show correlation between DOC concentrations in soil solution and soil texture. The lowest DOC concentrations were found in Oxisols on the plateaus with the highest content of clay in the transect. These low concentrations may result from adsorption of DOC to clay. The highest concentrations were observed in Spodosols of sandy lowlands, which probably results from higher permeability combined to low adsorption capacity. On the hillside, Ultisols of medium texture presented intermediate concentration when compared to the previous sites. COD migration is observed in all soil profiles, which is highlighted by higher concentrations of DOC in low lands at the 100 cm depth.