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Universidade Federal de Viçosa (2015)

Efeito do distúrbio na estrutura filogenética e funcional em comunidades vegetais da Caatinga ;

Mota, Nayara Mesquita

Titre : Efeito do distúrbio na estrutura filogenética e funcional em comunidades vegetais da Caatinga ;

Effects of disturbances on the functional and phylogenetic assembly of Caatinga plant communities in the northeast of Brazil

Auteur : Mota, Nayara Mesquita

Université de soutenance : Universidade Federal de Viçosa

Grade : Mestrado em Botânica 2015

Human activities cause impacts on plant communities and to measure their effects helps in the management and conservation of remnant patches. Thus, this study aimed to evaluate the biodiversity and the functioning of the Caatinga vegetation under disturbance effect, especially goats herbivory, at protected and unprotected areas. Sampling was conducted in the north of Bahia state, Brazil, along two roads under the same code - BR235 - (two situations of unprotected area), and the Biological Station of Canudos - EBC (one situation of protected area), where eight quadrats of 20 m x 50 m and four quadrats of 20 m x 50 m were plotted, respectively. In these plots, all woody individuals with ground-height circumference ≥ 10 cm and height ≥ 1 m were sampled. Non-woody species were sampled in two subquadrats of 10 m x 10 m within the larger quadrats of 20x50m. The basal area and the height of woody species, the relative coverage (CA) of non-woody species, were assessed. The species were classified according to the following functional features : the ability to sprout, to fix nitrogen, succulence with thorns, toxicity of vegetative structures, life form and endozoochory. For each situation and for the total sample were calculated taxonomic, phylogenetic and functional diversities of woody and non-woody communities. In addition, were analyzed the phylogenetic and functional structure of communities using Phylocom software 4.2. The phylogenetic signal of the studied traits was also evaluated, and mostly was converging, with exceptions. A Principal Component Analysis (NMDS) was conducted to verify the differences in the floristic composition and structure of woody component between protected areas and unprotected. The results indicate that exposure of vegetation to disturbance cause loss of species, and decrease in functions number. Furthermore, the nearby vegetation to the road comprises closest phylogenetically species, which also leads to a lower phylogenetic diversity. The protected area, the EBC, has a more overdispersed phylogenetic and functional structures than expected by chance, that means more biodiversity and functions. However, some results may come from multiple and concurrent processes between environmental factors and human disturbance. Thus, protected areas from the goat herbivory are essential to the maintenance of the Caatinga biodiversity and functioning.


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