Pedogenesis in a semiarid carstic environment at Limoeiro do Norte - CearÃ

• Autor(a) principal: Rodrigo de Oliveira GirÃo
• Data de Publicação: 2011
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UFC
• Texto Completo: http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=9401
• topic: CIENCIA DO SOLO

The soils formed on limestone rocks in semiarid climate of the Apodi Plateau show distinct characteristics of the rest of the state of CearÃ. In Apodi Plateau soils factors of soil formation are homogeneous, what suggests that this geomorphological formation sat up so the exposure time of the parent material of different soils is the same, the relief is homogeneous, the vegetation is caatinga across the Plateau and the distance between different profiles is small to suggest a possible change in climate, so it is supposed that the strong variations in soil classes are closely related to lithological variations. The Apodi Plateau in its Cearense portion covers four municipalities: QuixerÃ, Tabuleiro do Norte, Alto Santo and Limoeiro do Norte, the latter being the search location. The lithological constitution is predominantly limestone with different facies. It was established a transect with approximately 300 m, where observations were made by auger evaluations that allowed to select the locations of the five profiles. Morphological descriptions of the profiles were made and samples collection for physical analysis: granulometry, particle and soil density,determination of the gravel fraction, clay dispersed in water, quantity of nodules, and these were divided into five classes C1, C2, C3, C4 and C5, with diameter from 0.053 to 0.25 mm, 0.25 to 2 mm, 2 to 4.76 mm, 4.76 to 7.9 mm, 7.9 to 19.1 mm, respectively . Chemical analysis were to determine cation exchange capacity - CEC, phosphorus, total organic carbon - TOC, pH in water and KCl, selective dissolution of Fe in Citrate Dithionite Bicarbonate - DCB, Ammonium Oxalate and Sulfuric acid to determine the levels of total Fe, Al and Si in the clay fraction, and determine the molecular indices Ki and Kr. Three profiles were classified as Argissolos and two as Cambissolos. All the profiles showed significative quantity of nodules, which decreased in diameter yet increasing mechanical resistance as they neared the surface, where it had an aspect similar to "chumbo de caÃa." The data showed variations within and between profiles, such as the amount of gravel, which in one of the profiles of Cambissolos fell in the order of 780 g.kg-1 for 30 g.kg-1, a fact corroborated by the levels of Titanium, which indicate that such variations are due to different lithogenic origins. This allows us to conclude that among the factors of soil formation, parent material prints its characteristics as reflected in the different soil classes within a few meters between soil profiles and even a few inches of soil horizons.