Estudo da vegetação remanescente como subsídio à recomposição de áreas alteradas nas cabeceiras do rio Grande, Minas Gerais

Abstract

The objectives of the present study were (a) to describe the floristic composition of the arboreal vegetation of five forest remnants of the Itatiaia Mountain Range, SE Brazil; (b) to describe the arboreal vegetation of two two riparian forest environments (Slope and Alluvial) at different regeneration phases seeking to compare their structure, diversity, and species and guild composition (regeneration, dispersion and stratification); and to produce a species list to be used in projects aimed at the reclamation of altered areas in the Rio Grande Headwaters region. The species list resulted from floristic surveys carried out in five remnants of montane rain forest situated in the municipalities of Bocaina de Minas, Aiuruoca and Resende, followed by phytosociological surveys of three areas in Bocaina de Minas (between 22o10’–22o14’S and 44o28–44o33’W) in riparian forest environments (Slope and Alluvial) at different successional phases and along elevation gradients. Ten 400 m2 sample plots were laid off on a riverside alluvial terrace, another ten on a slope covered with a regenerating forest and 26 plots on a slope covered by preserved forest. All individual trees with diameter at breast height (dbh) ≥ 5 cm were identified to species and measured (dbh and height). The surveyed species were classified into regeneration, dispersion and stratification guilds. Variables related to soil chemical and physical properties, topographical features and successional phase, obtained for each plot, together with the species abundance data were used in direct and indirect gradient analyses. The direct analysis consisted of the comparison of the phytosociological data of the three remnants. The indirect analysis consisted of a detrended correspondence analysis (DCA) and a canonical correspondence analysis (CCA). The sample of the arboreal flora of the six forest remnants of the Itatiaia Range was composed of 450 species, 191 genera and 69 families, many of which are known as characteristic on montane forests (> 1000 m a.s.l). The tree flora of the Itatiaia Range forests is certainly among the richest areas of montane rain forests surveyed in SE Brazil. The three riparian forest remnants surveyed in Bocaina de Minas contained 286 species distributed into 144 genera and 61 families. With respect to the regeneration guilds, 68% to 75% of the species have propagules dispersed by animals (zoochorous), 15% to 19.5% are wind-dispersed (anemochorous), and 6% to 7% are dispersed through explosive dehiscence (autochorous). The Shannon diversity index (H’) and the Pielou evenness (J’) were 3.18, 3.53, 4.15, and 0.75, 0.76, 0.82, respectively, for the Alluvial, Regenerating Slope and Preserved Slope environments. The DCA showed a pattern of species differential distribution in the three environments related chiefly to ground water regime and forest successional phase. In addition, many species produced significant correlations between their abundance in the plots and variables related to soil moisture and to the succession rank, suggesting. Other species showed a wide distribution pattern, occurring from damp sites liable to floods to strongly drained slopes.