dc.creatorSchaefer, Carlos E.R.
dc.creatorDalrymple, John
dc.date2018-09-06T11:12:04Z
dc.date2018-09-06T11:12:04Z
dc.date1996-05
dc.date.accessioned2023-09-27T21:14:05Z
dc.date.available2023-09-27T21:14:05Z
dc.identifier0016-7061
dc.identifierhttps://doi.org/10.1016/0016-7061(95)00073-9
dc.identifierhttp://www.locus.ufv.br/handle/123456789/21669
dc.identifier.urihttps://repositorioslatinoamericanos.uchile.cl/handle/2250/8957052
dc.descriptionA 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.
dc.formatpdf
dc.formatapplication/pdf
dc.languageeng
dc.publisherGeoderma
dc.relationVolume 71, Issues 1–2, Pages 1-17, May 1996
dc.rightsElsevier B.V.
dc.subjectPedogenesis
dc.subjectSoils
dc.subjectRoraima
dc.subjectNorth Amazonia
dc.titlePedogenesis and relict properties of soils with columnar structure from Roraima, north Amazonia
dc.typeArtigo


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