Estrutura sinusial dos componentes herbáceo e arbustivo de uma floresta costeira subtropical

Abstract

As sinusias herbaceas e arbustivas sao componentes de comunidades florestais pouco pesquisados nas regibes tropicais e subtropicais. Neste trabalho foram estudadas a composicao floristica e a estrutura fitossociologica destas sinasias em uma floresta arenosa (restinga) da Planicie Costeira do Rio Grande do Sul, Brasil. Os dados fitossociologicos foram obtidos em 30 parcelas de 2 x 2 m. Em cads parcela anotou-se a presenca e a altura maxima das especies herbaceas e arbutivas, e a cobertura foi estimada pela escala de Causton. A composicao floristica total da area compreende 61 especies, 52 generos e 33 familias. As familias que apresentaram mais de duas especies foram: Poaceae, Commelinaceae, Orchidaceae, Piperaceae, Rubiaceae e Asteraceae. As formas de vida hemicript6fita e camefita foram as mais representativas. A amostragem fitossociologica resultou em 26 especies herbaceas e 10 arbustivas, pertencentes a 31 generos e 24 familias. As especies mais importantes foram Carex sellowiana Schlecht., Oplismenus hirtellus (L.) P. Beauv., Spathicarpa hastifolia Hook. (herbaceas), Pavonia sepium St.-Hil. e Justicia brasiliana Roth (arbustos). A diversidade e eqiiidade especifica, segundo os indices de Shannon (H') e Pielou (J) estimados pela frequencia, foram 2,98 e 0,84, respectivamente.

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 septum 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.