Composição e partição de nicho em gradientes de solo e luz no Cerrado

• Autor(a) principal: Tolentino, Gláucia Soares
• 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/123456789/2531
• topic: Gradiente ambiental; Partição de nicho; Cerrado; Environmental gradient; Niche partitioning; Cerrado; CNPQ::CIENCIAS BIOLOGICAS::BOTANICA

The Cerrado distribution occurs under vegetation types ranging from open fields with scattered shrubs to forest physiognomies, in a gradient of increasing fertility and decreasing soil acidity. Whereas it is expected the greatest similarity between areas with structural conditions and of similar land, this study was conducted in five Cerrado vegetation types which are distinguished by the type of soil and vegetation. At FLONA de Paraopeba, MG, plant species were sampled in 25 plots of 20 x 20 m, distributed in a transect in each of the following associations: cerrado sensu stricto on Yellow Cambisol; cerrado sensu stricto on Yellow Latosol; cerrado sensu stricto on Red‐Yellow Latosol; dystrophic cerrado on Red‐Latosol; mesotrophic cerrado on Red‐Latosol. In all plots soils were sampled to quantify N, Ca2+, Fe, Al3+, P, K, Mg2+ and organic matter. The ordination by principal component analysis and similarity analysis showed that samples of the same vegetation type are closer to each other, and all the cerrado sensu stricto are floristically and structurally similar, constituting a group closest to the mesotrophic cerrado and farther dystrophic cerrado. The lowest P, organic matter and N availability were found in cerrado sensu stricto. Mesotrophic cerrado showed the highest levels of Ca2+, Mg2+, P and K. The dystrophic cerrado had the highest average of Al3+, and its floristic peculiarity probably lies in the adaptation of plants to stress from high availability of Al3+, while its growth that have benefited from the high nitrogen availability. The Cerrado plant species are likely to have common attributes of specialization to a range of environmental gradients, whose distribution is limited in accordance with the minimum resources necessary for their persistence (R*). The objective was to define the niche partitioning between functional groups, rather than between species, from the analysis of the behavior of woody plants in response to the variation of soil nutrient and light resources. The availability of light was measured using hemispherical photographs. The names of functional groups were assigned according to the species ability to tolerate stress derived from the high availability of Al3+ in the soil or the ability to compete for light and nutrients. Species with Ni ≥ 20 were included in the functional group whose linear model showed better fit. Distribution of functional groups in response to environmental conditions (N, Ca2+, Fe, Al3+, P, K, Mg2+, organic matter and light) was measured by the method of spatial analysis by distance indices. The group of species Al tolerant (AT) consisted of four species and prevailed in high availability of Al3+, Fe and light, and low concentrations of Ca2+, Mg2+, P, organic matter and N. The species of this group have mechanisms of resistance to aluminum as adaptive strategy to their high saturation, but the investment in the maintenance of metabolic processes results in damage to plant growth. The AT group was mainly determined by N, and its distribution is negatively related to the availability of this mineral. The group of competing species‐calcicoles (CC) consisted of six species, and showed high density in low availability of Al3+, Fe and light, and high concentration of Ca2+, Mg2+, P, K and organic matter, suggesting a better definition of R*. These species lack mechanisms of resistance and suffering the toxic effects of Al3+, but have nutritional supply for investment in photosynthetic structures that ensure greater capacity to compete for light. Thus, it is emphasized that there is a tradeoff for the Cerrado species, in relation to the ability of aluminum tolerance and competitive ability. The groups that have adptive traits in association (ATC 1, ATC 2 and ASC) are most widely distributed and their R* was less defined, possibly because they consist of species with greater phenotypic plasticity. The species‐aluminum‐tolerant competitors (ATC 2) can be considered adapted to more intense adverse conditions, because support the stress from high concentration of Al3+ and the low availability of light at the same time. The semi‐competitors species (ASC) showed similar distribution to CC, but with less restriction from occurring. The ATC 1 group was weakly defined, since its aggregation was determined only by relation between light availability and Fe. Adjustments may be necessary to model that determines the species which compose this group.