Ambientes terrestres da ilha da Trindade, Atlântico Sul: Caracterização do solo e do meio físico como subsídio para criação de uma Unidade de Conservação

• Autor(a) principal: Clemente, Eliane de Paula
• Data de Publicação: 2006
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1625
• topic: Física do solo; Química do solo; Mapeamento do solo; Soil physics; Soil chemistry; Soil mapping; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::CIENCIA DO SOLO

Brazilian oceanic islands have great environmental importance, not only for its biodiversity, but also for its scientific value, due to geographical isolation. The Trindade Island stands out for being the most isolated and humid of the group of Brazilian oceanic islands. The main soils in occurrence of Trindade Island were studied, emphasizing their chemical, physical, mineralogical and peculiar micromorphological characteristics, in different environmental strata. Mapping of the island was done, producing thematic maps of geology, soils and geoenvironments. A preliminary proposal of zoning for environmental management was elaborated, based on thematic maps, foreseeing recovery zones in the degraded areas and specific protection in the primitive zones where vegetation still exists, containing endemic species of great ecological and environmental importance. This preliminary zoning proposal aim to subsidize the Conservation Unit management plan, now suggested. Furthermore, a better understanding of the pedogeomorphologic and vegetational relationships was achieved, allowing a preliminary outline of soil identification along the island expressive topographical variation. Ten soil profiles were collected, representing the main pedoenvironments resultant from variation of lithology, topography and vegetation many of them co-variants. Physical, chemical, mineralogical and micromorphological analyses were accomplished, as well as phosphorus fractions, organic matter and sequential extraction of metals of the samples for all the horizons of the collected profiles. The diversity of soils in the Trindade island is strongly related to variations in parent materials and geomorphologic/altimetric position. Generally, Trindade island soils present morphogenetic peculiarities that suggest their endemic character. They hold high natural fertility, little degree of natural weathering and very high values of available phosphorus and of calcium. The south face of the island, colder and more humid, has narrow ravines and gullies in steep hillsides that sposses exuberant vegetation of giant ferns, with accumulation of organic matter even in steep slopes, forming Histosols or Inceptsols, in more protected parts. The soils are more acid and more leached at altitudes higher than 400 meters, prevailing Inceptsols and Nitisols, although with very high phosphorus content. In the north, drier face of the island, lower areas have prevalent semi-arid or dry tropical weather, and the soils are shallower, riches in nutrients and with less organic matter. They are more eroded in the low lauds, prevailing Regolithic and Litholic Neosols. The sequential extraction data allowed two pedogenic environments to be distinguished: one of younger and less weathered soils, up to 450 m high; the second pedogenic environment was formed with soil from weathered parent materials, at altitudes of 450 - 600 m. The metals Cu, K, Mn, Ni and Zn were higher in the organic matter-bonded and to amorphous iron oxides fractions. The available content was very low in comparison with total content for all metals, dive to their presence in the mineral crystalline structure, seconded by organic matter and Fe compounds, amorphous or crystalline. The mineralogical analysis of sand fraction allowed the identification of large variety of primary minerals in the island s soils. These minerals show little natural weathering, conferring the high content of metals that are still observed, even in the clay fraction. Micromorphology aided the identification of some singular features in the island s soils, allowing the description of the microstructure and the composition. This analysis identified primary minerals that are still under alteration processes, in addition to intrinsic characteristics of each profile. Trindade s soils has particularities that make them difficult to fit into the Brazilian soil the classification system, demanding the creation of new classes at several categorical levels for the correct classification of Brazilian oceanic island s soils.