Caracteriza??o pedol?gica e g?nese de solos em duas topossequ?ncias no sistema c?rstico da Serra da Bodoquena (MS)

• Autor(a) principal: Silva, Marlen Barros e
• Data de Publicação: 2013
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UFRRJ
• Texto Completo: https://tede.ufrrj.br/jspui/handle/jspui/3201
• topic: Calcifica??o; Solos com carbonato de c?lcio; SiBCS; Calcification; Soils with calcium carbonate; Brazilian System of Soil Classification; Agronomia

Soil profiles were characterized in toposequences located in Serra da Bodoquena carbonate karts, Southwestern State of Mato Grosso do Sul, to elucidate the genesis of soils developed from carbonate lithology in tropical climate; to evaluate, by means of the soil phytolith assemblage, the influence of paleoclimatic conditions in the genesis of carbonate precipitation features; and to provide a better criteria for characterization and/or definition of calcic and petrocalcic horizons in the Brazilian System of Soil Classification (SiBCS). Nine soil profiles were selected, described and sampled along two toposequences, one at a plateau with slightly undulated relief and a long slope (T1) and the other in a strong undulated relief (T2). Analyses involved the physical, chemical, mineralogical and micromorphological characterization of soil profiles, and phytolith assemblage characterization. The results of the phytolith analyses suggest the occurrence of a drier climate at present in Serra of Bodoquena, after alternating periods of wet and arid conditions. The micromorphological analyzes corroborated this assumption, as evidenced by the presence of clays coatings around CaCO3 accumulations, coexisting with iron-manganese concretions. Under more humid paleoclimatic conditions the soils in T1 developed with similar attributes, such as reddish colors, increase in clay content with depth, and clay activity variable between 17 and 27 cmolc.kg-1. In the T2, the soils formed were least developed and had greatest variability of attributes. This was due mainly to the landscape unevenness, in the strongly undulating relief. Related to the diagnostic horizons, only in T2P1 and T2P4 profiles it was observed the calcic horizon, with the carbonate accumulations in T2P1 of lithogenic origin - formed under oscillation of the water table, and in T2P4 they were pedogenic. None of the profiles showed a layer with continuous hardening due to CaCO3 that would qualify as a petrocalcic horizon. According to the SiBCS, the T1P1 (footslope) and the T1P2 (backslope) profiles, respectively with sequence of horizons A-Bt and A-E-Bt, presence of weak to moderate clays films, and distinguishable polychrome, were classified as Argissolo Vermelho Eutr?fico t?pico (Typic Argiudoll) and Argissolo Vermelho Distr?fico t?pico (Typic Hapludult). The T1P3 (summit), with sequence A-Bi-C, was classified as Cambissolo H?plico Eutr?fico t?pico (Typic Humudept). In T2, the T2P1 profile located in a fluvial terrace and with CaCO3 equivalent levels much higher than required for calcic or petrocalcic horizons was classified as Chernossolo R?ndzico ?rtico t?pico (Mollic Fluvaquent). On the concave surfaces, the T2P2 and T2P3 profiles with A-Bt and A-E-Bt sequences, respectively, were classified as Luvissolo H?plico P?lico t?pico and Luvissolo H?plico ?rtico abr?ptico (Typics Hapludalfs). The T2P4 profile (backslope) showed a calcic horizon coincident with the C (sequence A-Ck'-R) and it was classified as Neossolo Lit?lico Carbon?tico t?pico (Lithic Udorthent). The T2P5 and T2P6 profiles, on the shoulder position and with A-R horizon sequence, despite the strong field effervescence with HCl 10%, did not fulfill the CaCO3 requirement for the calcic horizon, and they were classified as Chernossolos Eb?nicos ?rticos t?picos, respectively Lithic Hapludoll and Lithic Udorthent according to the Soil Taxonomy.