Geoambientes e relação solo-vegetação no norte de Minas Gerais

Abstract

This study identified, characterized and estimated the carbon stock of different geoenvironmental units that make up the Serra da Tenda, a representative landscape of the ecotonal context of northern Minas Gerais (Chapter 1); as well as evaluated the composition and structure of different plant communities and their relationship with altitude and soil physical and chemical properties along the same geoenvironmental gradient (Chapter 2). For the geoenvironmental stratification, the pedological, geomorphological and vegetational aspects were evaluated. Six soil profiles were described and collected. For the collection of composite soil samples (0-20 cm) and floristic sampling of shrub-tree species, eighteen 20 x 20 m plots were allocated. Soil samples were subjected to chemical and physical analysis, and these parameters were summarized by using Principal Component Analysis (PCA). The non-metric multidimensional scaling method (NMDS) was used. The floristic similarity, importance value index (IVI), Shannon-Wiener diversity (H’), Pielou’s evenness (J’) and indicator species (IndVal) indices were calculated. Canonical Correspondence Analysis (CCA) was used. Six geoenvironments were identified: (i) Dry Forest of Lowland on Eutrophic Oxisol (MSBX); (ii) Limestone Pavement with Cambisol (LAP); (iii) Dry Forest with Limestone Outcrop on Nitosol (MSAF); (iv) Dry Forest of Grota on Nitosol (MSGR); (v) Slope Cerrado on Cambisol (CENT); and (vi) Cerrado Encarrascado over Latosol in Chapada (CENR). There was a separation of geoenvironments due to edaphic characteristics and the occurrence of a fertility gradient. In Serra da Tenda, most of the soils are eutrophic, developed from limestone and pelitic rocks represented by the Bambuí Group, and the top is covered by debris-laterite (TQ) deposits from the Tertiary, characterized by dystrophic soils. The MSGR geoenvironment had the highest carbon stock (EC) in the soil. The geoenvironments analyzed showed great importance for the conservation of carbon in the soil. There are outcrops in limestone rock massifs with steep slopes, caves and limestone pavements. In the LAP there is a rocky vegetation of Lapiá (Limestone Pavement), in the higher portions the vegetation type is Cerrado (CENT and CENR) and the slopes and lowlands are covered by Dry Forest (MSBX, MSAF and MSGR). A total of 877 individuals were sampled, distributed in 111 species, belonging to 76 genera and 30 families. Fabaceae showed greater representation. The floristic similarity at the species level was considered low. Among the geoenvironments there are differences in the values of relative abundances. The Shannon-Wiener diversity index and Pielou evenness remained between 1.26-2.96 and 0.78-0.87, respectively. The indicator species analysis revealed that 25 species (22.5%) were indicators. The CCA analysis separated the species into 3 groups and, in general, indicated that the physicochemical variables of the soil and altitude provided differences in the floristic composition. Thus, from the uniqueness of each geoenvironment, in phytophysiognomic, topographical and edaphic terms, our study evidenced the high environmental heterogeneity, on a small spatial scale, of Serra da Tenda.