Padrões florísticos, estruturais e relações edáficas entre dois tipos de florestas tropicais estacionais no cerrado

Abstract

The present dissertation was elaborated in a form of two chapters developed in article structures. Foremost, a general introduction was quickly presented showing the current panorama about the tendencies of forest resources in which this research is included. In this item a general review about the concept of dry tropical forests in South America and Cerrado are also presented, concluding with a presentation of the structure that is divided in two chapters. Such chapters, are focused on a theme which is slightly approached at the present time in literature, the differences between the two main types of seasonally dry forests in Cerrado, the semi-deciduous seasonal forests and the deciduous seasonal forests. On the first chapter, the purpose was to explore how the edaphic factors could be determinant for the diversity and structure of the trees component of the two forests and, in order to do that, we chose to evaluate two very important edaphic parameters: fertility and soil water availability of the two stands. The study was developed in two fragments located at slopes of Araguari River, west of Minas Gerais. The results showed that those forests under the same environmental conditions (altitude, topography and rainfall) have different patterns of fertility and soil moisture profile, constituting in this way, the diversity, composition and horizontal and vertical structures of the stands, these last two parameters are strongly influenced by the differences in the succeeding levels between the two formations. On the second chapter, the purpose was to investigate whether exists a pattern of diversity and floristic composition in the arboreous component between the two seasonal forests in Cerrado. Were used, as a comparison, 10 seasonal forest areas already registered in the region of Triângulo Mineiro (five of each physiognomy), and through their data sets was possible to analyze richness, composition, level of species similarity, genre and family. As those 10 areas occur in different environmental conditions and variable distances, the two types of forests previous studied in the chapter one were added to the data set, because they represent the only examples of near physiognomies and similar environmental conditions. The results demonstrated that, in a general view for the 12 areas, don t matter the distance and environmental condition, the two physiognomies presented significant differences in the richness and floristic composition in the three taxonomic hierarchic levels investigated (species, genre and family). Forest fragments from the same physiognomy showed elevated levels of similarity and were also very similar in the three taxonomic levels, but when they were compared to two different physiognomies the results were significantly lower. It exposed that the patterns remain, indifferent to distance between the fragments. The data exhibited allowed to legitimate the physiognomic differences contained in the bibliography offering strong taxonomic and diversity patterns between the two physiognomies from Cerrado. The dissertation was concluded with the final considerations, which called the attention to the need of other researches which could confirm the hypothesis rose in this study in other seasonal forests of the Biome and in addition highlighted the importance of standard inventories to subsidize studies for recovering and rational use of forest resources from such ecosystems.