Análise da similaridade florística entre florestas do Alto Rio Xingu, da Bacia Amaz?nica e do Planalto Central

摘要

Recent studies have showed that the phytogeographic identity of the Upper Xingu River is as Seasonal Evergreen Forest. The region has peculiar physical and floristic characteristics, located at the contact area between the rain forest and the Brazilian Savannah (Cerrado). This study shows the floristic similarity between deciduous and semideciduous seasonal forests, cerrado of Middle Brazil and Amazonian tropical rain forests, aiming to interpret the relationship of the Seasonal Evergreen Forest of the Upper Xingu with one of these formations. Thirty-two lists of arbustive-arboreal species were taken from floristic and phytosociologic studies. The floristic similarity was estimated by Jaccard's index and the construction of dendrogram based on group mean values. The analysis of similarity allowed the identification of the clear floristic distinction between the Cerrado and the Amazon Forest biomes, as well as the areas of ecological tension between these biomes. The areas of seasonal evergreen forest were more similar to the monodominant semideciduous seasonal forest, which may be a consequence of their location in the ecotone between the Cerrado and the Amazon Forest. The low similarity between the Seasonal Evergreen Forest and the other forest types confirme the unique flora possessed by this phytophysiognomy, that demonstrates its recognition in a region considered as the transition area.