Diversidade de fitofisionômias e aspectos fisiográficos na região sudeste da Chapada Diamantina - BA, Brasil.

This study addresses the phytogeographic aspects of the southeast region of Chapada Diamantina - BA, especially a characterization of the phytophysiognomies, their relationships with climatic and physiographic factors, their spatial distributions and part of their floristic compositions. In addition, the relationship between phytomass and spectral data was analyzed and the geographic distribution patterns of some of the studied species were identified. In the study of phytophysiognomies, profile-diagrams were prepared with information on vegetation structure and floristic composition. Nine phytophysiognomies were studied: semi-deciduous seasonal forest, capon of semi-deciduous forest, cerrado field, dirty cerrado field, clean cerrado field, rupestrian field, caatinga, dry forest between the caatinga and the cerrado and the carrasco. The total basal area of the species of these phytophysiognomies ranges from 0.74m² in the semideciduous seasonal forest, to 0.01m² in the Campo Limpo, Campo Dirty and Campo Rupestre. The seasonal semi-deciduous forest has the largest size with almost 10% of the plants above 15m, while the Campo Limpo has the smallest size with more than 70% of the species smaller than 1m. The relationships between phytophysiognomies and climatic, topographical and pedological factors were studied. These relationships consisted of simple relationships with two variables and also multivariate. The average annual precipitation varies from 575mm, in the caatinga, to 1,291mm, in the semideciduous seasonal forest and in the campo rupestre, while the average annual temperature varies from 19.9°C, in the campo rupestre and in the seasonal semideciduous forest, to 23.8°C, in caatinga. Vegetation relationships with topography were performed using geoprocessing techniques. It was verified that most of the vegetation types in the region (61%) are located above 1,000m and not very related to a certain slope or slope orientation. Altitude was a more evident factor, showing, for example, that the caatinga appeared below the 900m elevation and the rupestrian field above 1,000m. Soil analyzes showed, in general, that they are very acidic and not very fertile soils. The best soils in terms of fertility were found in the caatinga, while the worst ones are found in the Campo Dirty. As for the depths, they are varied, being deep in the clean field, in the dirty field, in the executioner and in the semi-deciduous forest capon and, those shallow, present in the rupestrian field, cerrado field and in the caatinga. Multivariate analyzes with soil, climate, vegetation and spectral index data showed more complete relationships between the studied phytophysiognomies. The analyzes showed that seasonal semideciduous forests are closely related to humidity, the presence of organic matter in the soil and high cation exchange capacity and high potential acidity. The types of cerrado have close relationships with each other, while the campo rupestre on the one hand, and the caatinga on the other, show the extremes of relationships with other types of vegetation in the region. The ecotonal types, such as the carrasco and the dry forest between the caatinga and the cerrado, presented reasonable relationships with each other.The spatial distribution of vegetation was performed using geoprocessing techniques on LANDSAT-TM satellite images, in the IDRISI program. The phytophysiognomies were delimited in an image that combines red and near infrared bands (vegetation index) and through fieldwork (verification of the terrain truth). To prepare the vegetation maps, 6 classes of vegetation indices were created that correspond to one or more types of phytophysiognomy. Some of the classes of vegetation indices were separated, so that all the vegetation diversity in the region could be observed in the maps. Thus, 11 classes of vegetation cover were created: agriculture, caatinga, dry forest between the caatinga and the cerrado, cerrado field, dirty field, clean field, rocky field, executioner forest, low semi-deciduous seasonal forests including gallery forests, and greater size and mosaic of wooded savannas/low forests. The classes that predominate are low semideciduous seasonal forests/gallery forests and clean fields. With regard to floristic composition, 164 species were identified, 137 genera distributed in 60 families. Most of these species were exclusive to a given phytophysiognomy, with the carrasco vegetation having the highest number of species common to other types of vegetation. Most of the identified species have a wide geographic distribution pattern, encompassing provinces or entire regions of the Neotropical Kingdom. However, a considerable number of species are endemic to Chapada Diamantina. The relationships between phytomass and vegetation indices were high among grassland communities (campodirty, campo limpid and campo rupestre), while the relationships between total basal area and vegetation indices in all phytophysiognomies studied were lower.