Atributos químicos, físicos e mineralógicos dos solos e sua relação com os biótopos do Parque Estadual da Mata Seca, município de Manga, norte de Minas Gerais

Abstract

The extreme North of Minas Gerais is located in an ecotone zone between the biomes of Cerrado and Caatinga, a region with various biotypes which must be understood as a spacial expression of a geobiocenosis that contains biotic and abiotic elements. It is in this scenario full of various biotypes that the Mata Seca State Park is located. Aiming at a better understanding of the interaction among soil, plant, and society, the objective of this work is to analyze the influence of chemical, physical and mineralogical aspects of soil and of anthropogenic factors upon the floristic, physiognomic and structural characteristics of the vegetational components of the biotypes in the areas of study. In each biotype five portions of 15 m X 30 m (450 m2) were marked with 30 meters of interstice among them. In each portion all the live individuals with diameter at breast height were tagged and numbered (DBH = 1,30 m from the soil) 15 cm. The samples of the soil were chemically, physically, and mineralogically analyzed. The mineralogical analysis was done in the fraction of clay and in the fraction of sand. The technique used was the X-ray diffractometer (XRD). The data about the anthropic influence was obtained through interviews done with old employees from the farm where the park began. In the correlations between vegetation and soil, the technique of Canonical Correspondence Analysis (CCA) was used. Five classes of soil were identified. Most of them are eutrophic without aluminum in the solution, low in iron, with high concentration of Ca and Mg, with weak to moderate acidity and high clay activity (Ta). The X-ray diffractometer (XRD) showed predominance of quartz in the fraction of sand. In the clay fraction, the presence of kaolinite, illite, and montmorillonite was noticed in most portions of soil. The sulfuric acid attack highlighted that all the soil was low in iron. The pedological attributes were important, but not enough to differentiate the vegetational types, since all the soil portions are eutrophic and there are seasonal forests in different successional stages in the area. The anthropogenic factors, such as the selective cutting of species and the cyclic deforestation in the fields are the most relevant aspects in the explanation of the differences between the vegetational formations in the park. The vegetation in the Mata Seca State Park has such a rich floristic that it expresses itself within 83 species distributed in 25 families. The richest families in terms of floristic were the Fabaceae, the Bignoneaceae, and the Euphorbiaceae. These results show the evidence of the edaphic and anthropic effects upon the tree communities and still point that all the biotypes contain young trees undergoing successional processes at different ages. The CCA made it possible to group three vegetational contexts or sectors. The first sector is composed by Riparian Forest and the second is formed by Decidual Seasonal Forest in different successional levels. The third sector constitutes portions of the open shrubby Caatinga. In each sector there was a grouping of species generally found in edaphic environments correspondent to the respective areas.