Varia？？o das características pedológicas e classifica？？o taxon？mica de argissolos derivados de rochas sedimentares

there is lack of research on argissolos (ultisols and alfisols) in relation to theunderstanding of the pedologic variations. variations can be analyzed by multivariate statisticsand the data numerically classified. the comparison between the numeric classification andthe hierarchical classification can contribute to the evolution of the brazilian soil classificationsystem (sibcs). the aims of this research were to analyze the pedologic variation of argissolosderived from sedimentary materials in the central region of rio grande do sul and to validatethe organization of the order of argissolos in the sibcs based on the interpretation of thenumeric classification. forty-two profiles of argissolos in the central area of rio grande dosul were considered, derived from the formation santa maria and caturrita. the study wasbased on principal component analysis and cluster analysis. the principal component analysisindicated five components that explained 84.3 % of the data variance. these componentsare represented, from one to five, by the following variables: sand content, hue (color), basesaturation, clay activity and total organic c content. the cluster analysis separated the argissoloprofiles in three main groups. the drainage of the profiles in group a was deficient. theprofiles in group b were well-drained, but contained less clay and had a higher texture gradientand lower cation exchange capacity than group c with well-drained profiles, high al contentand higher clay content than the other groups. the numeric classification validated the structureof the sibcs for the order of argissolos. however, the cluster analysis detected importantmorphologic aspects that are not considered by the sibcs at a high categorical level (largegroup), e.g., variation in thickness and texture of the a or a + e horizon, clay content in the bhorizon and the textural gradient in the argissolo profiles.