Efeito de borda no componente arbóreo de um fragmento de floresta semidecídua, Viçosa, MG / Border effect on an arboreal component of a semideciduous forest fragment in Viçosa-MG

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

The objectives of this work were to characterize the arboreal vegetation structure, floristic composition and species diversity along the border-interior gradient of a forest fragment in Viçosa, Minas Gerais; to determine and characterize the canopy along this gradient; and to characterize the arboreal species distribution in the different successional categories. Thus, three 10 m equidistant transects subdivided into eight 5 x 5 m plots, 20 m spaced from each other, were installed from the edge of the fragment up to 180 meters towards its interior The transects were perpendicularly allocated at the edge of the fragment, extending up to its nucleus. All of the woody trees with stem diameter equal or superior to 10 cm were sampled and their heights estimated. Hemispherical photographs of the canopy were obtained, in the center of each plot, determining canopy opening and leaf area index (LAI). A total of 207 individuals belonging to 31 families, 63 genus and 85 species was sampled. The families with highest species richness were: Fabaceae with ten species; Myrtaceae with nine; Rubiaceae with six; Annonaceae, Lauraceae and Sapotaceae with five species. Variation in species richness did not obtain significant correlation with distance from the edge. Based on grouping analysis, it was possible to identify at least one group formed among the edge plots with those 25 and 50 m distant from the border towards the fragment interior. The Shannon diversity index was high (H = 4.00) with equability of Pielou (J = 0.9). No significant correlation was found between species diversity and distance from the edge. Significant differences in the diversity index values were verified between the plots located on the border and those presenting lower diversity index located 25, 50 and 175 m from the same border. Late secondary species occurred in larger number of species and individuals, compared to the other succession categories. Density of the pioneer species responded negatively and significantly to distance from the edge towards the fragment interior. Basal area and density values did not correlate significantly with border distance towards the fragment interior. Canopy height declined significantly as distance from the edge decreased, with height increase observed 50 m from the border becoming significantly different at 125 and 150 m from the border towards the fragment interior. Canopy opening revealed negative relationship with distance from the edge, decreasing significantly towards the interior of the forest. Canopy opening was significantly lower in relation to the border at 75 and 125 m towards the interior of the fragment. LAI lowest values were found on the edge plots while the highest ones were found 125 m towards the fragment interior. This study revealed changes in plant community along the border-interior gradient, suggesting a possible border effect 50 to 75 m from the forest border.

ASSUNTO(S)

fragmentação forest fragmentation border effect botanica efeito de borda ecologia da paisagem landscape ecology

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