1 Shrub thicket vegetation on tropical granitic inselbergs (French Guiana)

Abstract. In French Guiana, inselbergs are granite outcrops rising abruptly from the surrounding rain forest. They constitute isolated islands of a special type of vegetation restricted to this peculiar substrate. Shrub granitic vegetation, organised in thickets on open exposed rocks of inselbergs, are described using the Braun-Blanquet method combined with numerical analysis (Correspondence Analysis). This phytosociological study revealed only one particular shrub community on each inselberg, including predominantly evergreen and sclerophyllous shrubs, especially microphanerophytes, belonging to Clusiaceae, Myrtaceae and Bombacaceae. These insular outcrop communities exhibit species endemic to the Guianas region and also species rare in French Guiana. Affinities with flora of other inselbergs and vegetation types in South America are examined and discussed. Reasons for observed floristic and structural changes in each community are also discussed