Gênese, formas de carbono e sílica biogênica de solos sob Formações Estacionais do semiárido de Minas Gerais e Bahia

• Autor(a) principal: Martins, Carolina Malala
• Data de Publicação: 2012
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1635
• topic: Florestas Estacionais Deciduais; Matas Secas; Corpos silicosos; Deciduous forests; Dry forests; Silica bodies; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::CIENCIA DO SOLO

Deciduous forests, commonly known as dry forests, have been at the center of discussions between society, environmentalists and farmers. These discussions revolve around differing legal definitions of deciduous forests, such as the formations of northern Minas Gerais, which are considered part of the phytophysiognomy of the Atlantic Forest at the federal level but treated as a unique ecosystem at the state level. Dry forests can be found in the form of patches throughout different domains, predominantly occurring in outcrops of limestone, siltstone and slate, as well as in entisols, ultisols, cambisols and oxisols. Their deciduous foliage, a principle consequence of the climatic seasonality to which they are subjected, characterizes these formations that present a short wet period and long dry period. Starting from this conflict of ideas and questions, the present work aimed to describe soils under deciduous formations through the description and classification of representative soil profiles (Chapter 1). The aim of Chapter 2 was to find specific attributes that represent soil changes that occurred in deciduous forest soil, using soil organic matter and its fractions in order to understand its behavior. In Chapter 3, we aimed to identify possible predominant vegetation of deciduous forests by identifying silica bodies in the soil, in addition to detailed studies of the composition of xerophytic plant ashes to understand their possible adaptation mechanisms in this environment. We performed chemical, physical, and mineralogical analyses on 10 profiles of deciduous forest soils (Chapter 1); performed chemical MOS fractioning and obtained their oxidizable fractions (Chapter 2); performed optical and electron scanning microscopy of silica bodies in studied silt soil profiles, determined dry matter content of the dominant xerophytic species and obtained the ashes of these species under acidic and basic conditions, as well as distilled water, to determine the elements Si, Ca. Mg, P, Fe and Al (Chapter 3). Deciduous forest soils are eutrophic and geologically heterogeneous, in addition to having varying degrees of weathering, with soil classes ranging from oxisols to entisols with predominantly ilitic and kaolinitic mineralogy. The humic substances that compose the organic matter of the soil profiles of deciduous forests indicated that the MOS compartment showed a predominance of humin fraction, followed by humic acids and lower C content, with fulvic acids for most soils. The different fractions of oxidizable C were able to associate more labile fractions with superficial horizons, and more recalcitrant fractions with subsurface horizons. The identification of silica bodies in deciduous forest soils was low, but siliceous structures were detected and the most common morphologies were rod and bulliform type phytoliths. In some soils, rods showed corrosion and coating by iron oxide and aluminum. However, it was not possible to distinguish deciduous forest areas from others by the presence of silica bodies. Studied xerophytic plants showed elevated ash levels in relation to dry matter, indicating the presence of a large quantity of inorganic substances in such species. The X-ray powder diffraction of insoluble ash showed intense peaks of calcium carbonate and magnesium carbonate formed during the calcination process of the studied plant species.