Ecologia funcional e padrões de alocação de alumínio e nutrientes em plantas lenhosas do Cerrado

• Autor(a) principal: Nascimento, Márcia da Silva
• Data de Publicação: 2011
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/2536
• topic: Grupo funcional; Estresses; Alumínio; Functional group; Stresses; Aluminum; CNPQ::CIENCIAS BIOLOGICAS::BOTANICA

The Brazilian Cerrado is one of the world's largest tropical savannas in scope and in terms of biodiversity. The occurrence of the Cerrado is determined by climatic factors, but a strong relationship between soil types and the overlying vegetation has been observed. Nevertheless, the functional ecology of the Cerrado and the establishment of functional groups are still poorly studied. This study aims to establish functional groups of plant species from the Cerrado and discuss the results on the basis of two theoretical approaches: Grime (1977) classifies the plants due to its occurrence in different environments into functional groups as competitors, stress tolerators and ruderals (C-S-R triangle theory). In his (R*-model) resource competition theory, Tilman (1984) reflects about potentially competing species causing the competitive exclusion of species less adapted because of more effective resources exploitation. The presented study was realized at Paraopeba National Forest, MG, where five different vegetation-soil combinations were studied: Mesotrophic and distrofic Cerradão, two forms of savannah woodland, both above Red Latosol; typical savannah vegetation, so-called Cerrado sensu stricto, was found above Cambisol, and Red or Yellow-Red Latisol. In each combination, five permanent plots of 20 x 20 m were established. All trees with a circumference at ground level greater than or equal to 10cm within the plots were identified. In each plot, soil sample were collected with three repetitions totalizing 75 samples. 23 species were selected, presumably forming different functional groups. Leaves, roots, wood and bark were collected from five individuals from each species selected to evaluate mineral composition. Concentrations of phosphorus (P), potassium (K), calcium (Ca2+), magnesium (Mg2+), aluminum (Al3+), nitrogen (N) and iron (Fe2+) were analyzed. By correlations between different soil properties and their abundance, species were classified into four functional groups from the best fit of the data to four mathematical equations: (1) MOxCa = Calcicole-Competitors (CC) consisting of the species Rhamnidium elaeocarpum, Luehea divaricata, Myracrodruon urundeuva, Casearia rupestris Dilodendron bipinnatum and Magonia pubescens; (2) MO-Al2 = Competitors Semitolerators Aluminum (ASC) established by Alibertia edulis, Myrcia tomentosa, Protium heptaphyllum, Myrcia splendens; (3) AB3x(Al/2) = Competitors Tolerators Aluminum (ATC) constituted by Vochysia tucanorum, Terminalia argentea, Pera glabrata, Siparuna guianensis Salvertia convallariodora, crassiflora Annona, Xylopia aromatica, Tapirira guianensis Astronium fraxinifolium, and Erythroxylum suberosum; and (4) Al3xMO2 = Tolerators Aluminum (AT) with the species Byrsonima crassifolia, Eugenia dysenterica, and Curatella americana. The stoichiometric analysis showed little difference in the allocation of nutrients and aluminum. The groups ATC, ASC and TA that are better suited to low soil fertility, show different stoichiometric patterns in the accumulation of Fe+2, P, K and Ca+2 in leaves and K, P, Ca+2 and Mg+2 at the root compared to species from the CC group. Species from group ATC accumulate a lot of aluminum throughout the plant. They also show higher N concentration in roots than AT and ASC (the other groups tolerant to Al+3). CC, in contrast, shows an accumulation of Fe+2 in leaves. The C-S-R triangle theory from Grime can be applied to the Cerrado vegetation, especially because groups show primary strategies, such as stress tolerant of aluminum toxicity (AT), and secondary strategies, with the competitors semitolerant aluminum (ASC) and the competitors tolerant aluminum (ATC). The largest amount of N in the roots has been found in the species of group ATC, the functional group with highest growth in acid soils, showing that greater investment in roots keep the plant growth positive in soils with nutrient deficiencies. This supports the predictions of the resource competition theory from Tilman. Therefore, both theories are likely to address the functional ecology of the Cerrado.