Gênese de luvissolos ao longo de uma climossequência sobre anfibolito no semiárido de Pernambuco

Abstract

The Luvisols are considered as a grouping of soils with textural B, clay fraction of high-activity clays, high base status. They are soils with evolution according to the performance of the bissiallitization process combined with the production of iron oxides and the mobilization of clay from the superficial horizon, with accumulations in subsurface horizons. Studies in Luvisols have indicated the formation of clay in situ (argilation) as the main process of formation of Bt, however other processes such as argiluviation and lithologic discontinuity may be of comparable or greater importance in the creation of textural contrast, which characterizes this grouping of solos. In the semi-arid region of Pernambuco, bissiallitization becomes the predominant weathering path, with predominance of clay minerals 2: 1 (smectite and illite), 1: 1 (kaolinite), with illite interstratified with smectites. Fersiallitization and rubification were described as the most outstanding pedogenetic processes. Thus, this study sought to understand the genesis of clay minerals and texture contrast of Luvisols of the semi-arid region of Pernambuco (Brazil), evaluating the morphology, mineralogy and micromorphology along a transect in the semi-arid formed from the amphibolite alteration, as well as classify soils according to the Brazilian Soil Classification System (SiBCS) and WRB / FAO. The following characteristics were considered: being inserted in the semi-arid Pernambucano, native or secondary vegetation, without any kind of influence or anthropic action, mafic metamorphic crystalline basement (particularly amphibolites). The micromorphological analysis of the thin sections indicated no pedofeatures of clay illuviation thus the formation of clay in situ (argilation) responsible for the texture contrast in these profiles. Profile 1 located in Itacuruba (PE) was classified as Luvissolo Chromic Ortic vertissolic solodic saline (WRB- Chromic Vertic Luvisol (hypereutric, protosalic, sodic)), profile 2 as Luvissolo Chromic Ortic vertissolic (Chromic Vertic Luvisol (hypereutric)) and profile 3 as Luvissolo Chromic Ortic typical (Chromic Luvisol (hypereutric)). Profile 1 did not fit into a class cataloged in SiBCS, constituting a new class of Luvissolo.