Restingas do Estado da Bahia: riqueza, diversidade e estrutura

Abstract

Restingas (tropical coastal vegetation) are located on the coastal plains, with species from adjacent ecosystems found throughout the Brazilian coast. The coast of Bahia is housed in two geomorphological sectors of the Brazilian coast: the Northeast Coast and the East Coast, with different climatic and geomorphological features. There are few information about the coastal vegetation of Bahia and becomes necessary to study about the composition and structure of vegetation from the coastal area. This study aimed to characterize the structure of the six areas of restingas distributed on the coast of Bahia, located in the towns of Massarandupió, Diogo, Ituberá, Serra Grande, Trancoso and Caravelas, and it is divided into two articles: the first article presents the structure of the vegetation by the quadrant method, to test the hypothesis that the structural composition of vegetation is influenced by the edaphic factors and geomorphological formation. Soil samples were collected to analyze the chemical and physical soil variables. The phytosociological survey resulted in 185 species belonging to 56 families. The areas showed heterogeneity at the structure and composition of the flora, with the majority of individuals with heights ranging from 1.0 to 6.0 m and diameters between 3-13 cm. The family more often founded among the areas was Myrtaceae and the species with the highest VI was Myrcia ramuliflora. The Shannon diversity index (H') of areas (2.769 nats.ind-1 to 3.553 nats.ind-1) was similar to other restingas from the Northeast especially Trancoso had the highest value (3.553 nats.ind-1.). The CCA analysis showed that species in the areas of restingas from Bahia, are influenced by some soil variables (aluminum, sodium, phosphorus and clay) and the faces of closed forest not flooded and non-flooded open fruticetum allowed defining two groups located in distinct geomorphologies. The second study tested the hypothesis that the restingas from Bahia lack floristic similarity with the other northeastern states due to abiotic and geomorphological factors. Lists of species from phytosociological studies of 16 areas of restingas were compiled – six developed in Bahia and 10 studies conducted in other Northeastern states, using the same methodology in obtaining structural data. Was assembled an array of floristic presence/absence with 195 species, to calculate the Jaccard index, grouping and sorting through the Analysis of Multidimensional Scaling (MDS). We used the latitude associated with wealth and diversity of each area to assess a correlation between the restingas along the northeastern coast. The highest wealth level was found in restingas located at south of Bahia, Alagoas and Pernambuco. The restingas of Bahia showed low similarity with the restingas from other northeastern states. There were significant differences in the association of latitude with the values of diversity; and species wealth with latitude between the restingas from Northeast. The areas formed groups with significant differences of similarity, thus demonstrating heterogeneity of northeastern restingas regarding wealth and diversity.