Heterogeneidade do substrato e suas relações com a comunidade arbustivo-arbórea do cerrado na Cadeia do Espinhaço

Abstract

The objectives of this work are: (a) evaluate the floristic, structural and environmental similarities of three savannah areas sampled in Upper Jequitinhonha Valley, inserted in the Cadeia do Espinhaço, Minas Gerais: area 1- Rio Preto State Park (PERP) in São Gonçalo do Rio Preto; area 2 - Biribiri State Park (PEB) in Diamantina and area 3 – Guapuruvu Reserve (RG) in Itamarandiba; Minas Gerais, in order to contribute to the knowledge of the patterns of regional flora; (b) to verify how the rock outcrops have influence on the ecological patterns of shrubs and arboreal species of an area of rocky stricto sensu savanna in PEB and go through the existence of indicator species in a specific type of ambient related rocks; e (c) evaluate the correlations between the distribution and density of shrub and arboreal species with the environmental variables and realize based on this correlation, a stratification of the area and describe the floristic composition and the total community structure and for each ambient formed in the fragmentation of the area of savannah stricto sensu studied in PERP. Plots of 20 х 50 m (1,000 m2) were located by systematic form, with seventeen plots in area 1 (PERP), ten in area 2 (PEB) and nineteen in area 3 (RG), totaling the sample areas with 1.7 ha, 1.0 ha and 1.9 ha, respectively. In these plots, recorded all living shrub and arboreal individuals that attended to the inclusion criteria, diameter at 0.3 m above soil (DAS) ≥ 5 cm. In the three areas were collected ten single samples of topsoil (0-20 cm of depth) in each plot, to obtain a randomly compound sample of 300cm3. In PEB were collected information on the cover of rocks in each plot. In PERP was realized the georeferencing and of the relief survey of the plots and anthropic and natural events were observed per plot and utilized to compose the environmental variables group with the soil and relief variables. There were registred in three areas of savannah stricto sensu 5.078 shrub and arboreal individuals, where 1.651 in PERP (971,18 ind.ha-1), 440 in PEB (440 ind.ha-1) e 2.987 in RG (1.72,11 ind.ha-1), totaling 118 species in 78 genera and 42 botanical families. The areas 1 and 2 are the most similar according to results Detrended Correspondence Analysis (DCA) and Principal Component Analysis (PCA). In the aggrouping analysis (dendogram) e DCA performed with ten plots of the PEB, show that these are divide into two groups of according with rock outcrops covering within some of these plots; according to the indicator species analysis (ISA) in the analyzed species, four had significative preference to ambient with non existence of rock outcrops and three with the ambient with rock outcrops. In PERP the Canonical Correspondence Analysi (CCA) presents five distinct ambient, with the greater influence of the correlation among the species distribution and the environmental variables: shallow soils, % of sand, pH and t. Each ambient showed a different group of species with higher VI, and the ambient 1 and 5 were the dissimilar ones by the Jaccard analysis (Sj).