A vegetaÃÃo em afloramentos rochosos no semi-Ãrido: diversidade e respostas ao ambiente

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

The objectives of this work were to analyze the floristic composition and the vegetation structure in two rocky outcrops, located in the semi-arid of PE, Northeast of Brazil. Also was tested the possible relationships between the studied vegetation and four environmental variables: area, soil depth, inclination of the rock and locality. This work documents 201 species of vascular plants, where Fabaceae (18spp. ; 9%), Asteraceae (17 spp. ; 8.5%), Orchidaceae (13 spp. ; 6.5%), Euphorbiaceae (12spp. ; 6%), Bromeliaceae (10spp. ; 5%) and Poaceae (8spp. ; 4%) were the families with bigger number of species. Three of species recorded are restricted the rocky outcrops of the region. Were found 1795 individuals of 63 taxons. The majority of the species that had presented many individuals had frequency low in the parcels and vice versa. The similarity of Jaccard between the localities was 0,347. The values of the diversity index had been H: 2,572 and H: 2,547 nats/individual. The area is only factor that significantly influences the richness and the abundance, however is not significant for composition. This showed to relation with all the other variables. Thus, the species present definitive preferences for type of topography and soil depth. The families who had predominated in the flora are also common and rich in outcrops and also in the vegetation of the surrounds. However, the presence of restricted species is indicative of the peculiarity of these environments. Comparing the value of the index of similarity with the ones of other studies, it can be inferred that the two areas belong to the same flora. The diversity is comparable the outcrops and the herbaceous vegetation of the region. Islands of vegetation with higher area present peculiarities that allow that they present more species, as higher amount of micro-sites. On the basis of the multiple regression and in the CCA, the inclination and the soil depth possibly don’t determine how many species and how many individuals will colonize island, but which will be these species. This relationship enters the flora with the topography and the soil characters it supports many descriptive comments in rocky outcrops. However, as the CCA sample that the more percentage of the variation of the species is explained by the locality, probably external variable must be also affecting the vegetation

ASSUNTO(S)

inselberg inselberg caatinga ilhas de vegetaÃÃo botanica vegetation island caatinga

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