Pedogenesis and relict properties of soils with columnar structure from Roraima, north Amazonia

Show simple item record Schaefer, Carlos E.R. Dalrymple, John 2018-09-06T11:12:04Z 2018-09-06T11:12:04Z 1996-05
dc.identifier.issn 0016-7061
dc.description.abstract A toposequence of soils with columnar structure in the Paricarana catchment (Roraima State, north Amazonia) was studied. The soils occur within the driest part of tropical Amazonia. The two soils in the lower positions are magnesic, as well as sodic, displaying columnar structural peds. The upper slope position is calcium-saturated, associated with dry forest, whilst the the Mg/Na affected soils are associated with xerophytic savanna. The whole toposequence is being progressively acidified and leached (the solodization process), from the upper slope position to a maximum at the bottom of the toposequence. In spite of the high amounts of total Na,O in all three soils due to the presence of Na-plagioclase, the exchangeable level is concentrated in the lower slope positions, thus creating abrupt changes between the columnar Bt and the overlying A and E horizons. Morphologically, the resulting structural patterns of columnar peds are thought to reflect the effects of exchangeable magnesium plus sodium, more than sodium itself. The little variability in total amounts combined with large variability in the exchange levels suggest that differential redistribution of Na and Mg by overland-flow, throughflow and groundwater fluctuations is responsible for such Na/Mg accumulation in the bottom of the landscape. The present climatic regime, although seasonal, ought not to favour the presence of sodium/magnesium affected soils in this part of Amazonia. They possibly represent relict soils from former semiarid climates in north Amazonia, showing features of the degradation process currently underway. en
dc.format pdf pt-BR
dc.language.iso eng pt-BR
dc.publisher Geoderma pt-BR
dc.relation.ispartofseries Volume 71, Issues 1–2, Pages 1-17, May 1996 pt-BR
dc.rights Elsevier B.V. pt-BR
dc.subject Pedogenesis pt-BR
dc.subject Soils pt-BR
dc.subject Roraima pt-BR
dc.subject North Amazonia pt-BR
dc.title Pedogenesis and relict properties of soils with columnar structure from Roraima, north Amazonia en
dc.type Artigo pt-BR

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  • Artigos [634]
    Artigos Técnico-científicos na área de Solos

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