The herb and shrub synusiae are little known components of forest communities in tropical and subtropical regions. The floristic composition and phytosociological structure of these synusiae were studied in a dune forest (restinga) of the Coastal Plain of Rio Grande do Sul, Brazil. Synusial composition and structure were recorded for 30 sample plots of 2 x 2 m. In each plot, presence and maximum height for herb and shrub species were recorded, and cover was estimated according to Causton's scale. There were 61 species, 52 genera and 33 families in the area. Families with more than two species were: Poaceae, Commelinaceae, Orchidaceae, Piperaceae, Rubiaceae and Asteraceae. The life-forms of most species were hemicryptophytes and chamaephytes. The phytosociological sampling resulted in 26 herbaceous and 10 shrubby species, pertaining to 31 genera and 24 families. The most important species were Carex sellowiana Schlecht., Oplismenus hirtellus (L.) P. Beauv., Spathicarpa hastifolia Hook. (herbs), Pavonia sepium St.-Hil. and Justicia brasiliana Roth (shrubs). Species diversity and evenness, using Shannon's (H') and Pielou's (J) indexes estimated from frequency, were 2.98 and 0.84, respectively.
Herbs; shrubs; restinga; diversity; life-forms
