Effects of slope orientation on pedogenesis of altimontane soils from the Brazilian semi-arid region (Baturité massif, Ceará)

Abstract

Given the importance of climate conditions for the development of soils, studies on climosequences are a valuable tool to predict the influence of climate change on weathering rates and on soil formation processes. The Baturite massif, a humid enclave located in the Brazilian semi-arid region, has unique characteristics that cause a disproportional distribution of rainfall: the eastern and northern slopes receive more than 1,600 mm/year of rainfall, whereas the southern and western slopes have semi-arid characteristics with rainfall of less than 600 mm/year. Eight soil profiles were selected to investigate the influence of these distinct climates on soil formation. To achieve this, physical, chemical, morphological, mineralogical and micromorphological data were determined and analyzed. In the humid slope predominate soil processes include melanization, brunification, intense leaching, acidification and alitization, with intensified weathering in higher altitudes. In contrast, the environment in the dry slope favored the occurrence of soils with a higher base status, high-activity clays, low Al saturation and bisialitization processes coexisting with monosialitization, mainly in the soils located at lower altitudes. Micromorphological data indicate that clay illuviation is not the main process responsible for the enrichment of clay in the subsurface horizons. The contrasting environmental conditions with different mineralogical composition seem to be an important indicator of weathering intensity and pedoenvironmental conditions.