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Acta Botanica Brasilica
versão impressa ISSN 0102-3306
FINOTTI, Ricardo; KURTZ, Bruno Coutinho; CERQUEIRA, Rui e GARAY, Irene. Variations in structure, floristic composition and successional characteristics of forest fragments of the Guapiaçu river basin (Guapimirim/Cachoeiras de Macacu, RJ, Brazil). Acta Bot. Bras. [online]. 2012, vol.26, n.2, pp.464-475. ISSN 0102-3306. http://dx.doi.org/10.1590/S0102-33062012000200022.
This paper presents an analysis of the composition and structure of plant assemblages of forest fragments with different characteristics (in relation to the type of rural properties in the surrounding area, size and disturbance history) and an area located within a Conservation Unit (control area) in the Guapiaçu river basin. In each fragment, two plots of 50 x 100m were delimited to the South and West, the height and DBH of all trees with DBH ≥ 5 cm were measured, and the individuals were identified to the lowest possible taxonomic level. The density, basal area and diversity were calculated and the DAP values and proportion of individuals in the diameter classes were compared between the assemblages. The phytosociological parameters were also calculated and twenty species of higher coverage indices were selected to compare the species composition and their successional characteristics. All assemblages studied had high species richness and species diversity. However, when compared to the control, all of them had significant differences in at least one of analyzed characteristics. All had a lower proportion of individuals in the largest diameter class and late secondary species. However, these differences did not corresponded to differences in the comparisons of individual DAP values. Some assemblages had DAP values equal to or higher than the control area. In fact, within some fragments, the higher proportion of individuals in the intermediate diameter classes contributes more to the total basal area value. In general, there was a greater abundance of pioneer and early secondary species in the forest fragments, but the proportion of these successional groups varied between them, showing the subtle differences in the successional stages that these fragments are in. These differences could be related to some variability of the environmental disturbances identified. Based on the results, it was found that the forest fragments surrounded by small farms are in initial successional stages and have been subjected to severer disturbances.
Palavras-chave : forest fragments; successional stage; diameter classes; disturbances; phytosociology.