An attempt is made to summarize what is known about the richness of the total terrestrial angiosperm flora of the "cerrados" (as a complex of formations) in Brazil, based on published surveys and species lists. A "refined" list of arboreal and shrubby species was compiled from a total of 145 individual lists from 78 localities, taking into account synonymy and recent taxonomic changes. The refined list had 1709 references to taxonomic entities at the species level (973 identified with confidence and 31 with aff or cf.), 572 references to generic entities (363 genera identified with confidence), and 210 references to the family level (88 families identified with confidence). There are many unidentified arboreal and shrubby taxa at the specific, generic, and family levels, indicating that a considerable amount of taxonomic research remains to be done on the cerrado flora, and that this flora may be much richer than is generally assumed. Depending on the assumptions made, these data suggest a total of around 1000 to 2000 arboreal and shrubby species and 2000 to 5000 herbaceous ones, yielding estimates for the total cerrado flora (terrestrial angiosperms) ranging from 3000 to 7000 species. These limits, especially the upper one, are dubious, but give an idea of the magnitude of the angiosperm flora in the Brazilian cerrados. Surveys of cerrados are very unevenly distributed, and studies of relatively unknown sites may reveal much more diversity than that presently known.

RESUMO - Palavras-chave: fitossociologia, ecótono, Campo Maior, Piauí ABSTRACT -(Phytosociology in parts of vegetation from Campo Maior Complex in Campo Maior Municipality, Piauí State, Brazil).With the purpose to contribute to the knowledge of the phytophysionomy of transition in a area in Campo Maior province, recover for a vegetation denominated Complex of Campo Maior, utilized the Quadrants Method considering all stem diameter of ≥ 3cm at the soil level. They were allocated 100 points in each area, Alto do Comandante and Baixão da Cobra, located in Lourdes' Farm. Were showed 46 species in Alto do Comandante and 44 in Baixão da Cobra, in a total of 68 species. The density values and of basal area were 2,730 and 2,799ind ha -1 and 38.22 and 38.58m 2 ha -1 , respectively. The species with major rate of importance value (IVI) in Alto do Comandante were Casearia ulmifolia Vahl. ex Vent., Aspidosperma subincanum Mart., Combretum leprosum Mart. and Bauhinia ungulata L. The first position of C. ulmifolia was in consequence of three relative parameter. Only three species of major IVIs contributed with the majors rate of covering value (IVC). In Baixão da Cobra, the specie of major IVI was Aspidosperma subincanum Mart, also in consequence of three relative parameters values. Combretum mellifluum Eichler, Bauhinia pulchella Benth. and Buchenavia capitata (Vahl.) Mart. also stood out. The four species with major IVI corresponded with that ones of major IVC. The rates of diversity of Shannon (H') was 3.20 and 3.09nats ind -1 to Alto do Comandante and Baixão da Cobra, this values can be considered high when compared with the values found in works developed an Caatinga, Carrasco and Cerrado Brazilian Northeast.

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Cerrado vegetation covers about 33% of the total area of the state of Piauí, northeastern Brazil, where there are also large areas of transition and contact with other vegetation types. Although the Piauí cerrados are a direct northern prolongation of the central core area, they are considered marginal by almost all authors. There are few previous records of their woody flora. This paper presents a floristic list of woody species based on the survey of 11 localities and updating of two already published lists. The climate belongs to Thornthwaite's subhumid category due to Piauí's position between the semiarid northeastern domain and the superhumid Amazon. The annual total rainfall is similar to that of the major part of the Brazilian cerrado area, but the rainy season is shorter. The soils differ from most cerrado soils in containing a greater proportion of concretions and plinthite with generally lighter colours, which may be interpreted as indicating large fluctuations of the water-table during pedogenesis. There are also widespread indications of seasonal high water-table showing that many of the Piauí cerrados probably belong to Sarmiento's hyperseasonal savannah category. A total of 60 families is represented by 307 woody taxa (including 14 family indet., four genera indet. and 80 species indet.). The lowest floristic diversity (richness) occurred in pure cerrado, the greatest in transition and contact areas.

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