Ciclagem de fósforo e suas variações em uma floresta madura da Amazônia central

Abstract

Little is known about phosphorus (P) variations tropical ecosystems due to shortage of soil P information and standardized methods for the quantification of cycling. The theoretical model of P cycling (Walker and Syers, 1976) suggests that the relationship between the contents and form of this macronutrient is closely linked to the stage of soil weathering, with this acting on the transformation of primary minerals (calcium phosphate) in other forms of P used by the biota or occluded in the soil; such as adsorbed in the surface of secondary minerals (Fe and Al), and P lost through leaching. The Hedley fractionation method provides a comprehensive assessment that has been widely used for P research. Aiming to quantify the flow P, soil samples were collected in the Reserva Florestal Adolpho Ducke in Manaus, Amazonas, Brazil, in five randomly selected plots. We investigate the forms present in soil and litter and the production of litterfall and its relation to P fractions during the transition between wet and dry season. This study suggests that there is a strong temporal variation between inorganic and organic forms of P, especially in the more stable fractions (NaOH). Production of litterfall indicate that the more stable fractions are strongly related NaOH and HCl to the dynamics of the fractions in the soil, through the entry of P.. This study is a pioneer as the cycling of P in soils of central Amazonia. Others studies are necessary to improve our understanding of the temporal dynamics of P in tropical soils.