Woody islands in South Brazilian coastal grasslands: effects of spatial variations on the structure of plant communities

Brazilian costal sand plains ( restingas ) are widely known for their many vegetation types, often responding to small landform variations which in turn cause quite distinct soil conditions. One interesting and still poorly known physiognomy is the woody patches or islands dispersed over sparse to dense herbaceous matrixes. Our main objective in this paper was to assess how spatial variables, as area and volume of the patches, affect the floristic composition and the community structure of woody patches in south Brazilian coastal grasslands. We analyzed 48 woody patches in four study sites in central coastal Rio Grande do Sul, Brazil. Each woody island was measured, and all vascular plant species above 30 cm were registered and quantified according to an abundance scale. Each species received values from one to five depending on the occurrence in five possible segments of each woody patch. Woody patches varied roughly between 4 and 204 m 2 . The floristic inventory resulted in 102 species in 49 families, Myrtaceae and Bromeliaceae being the most diversified, with eight and seven species, respectively. A total of 12 life-forms were recognized, the most diversified being trees or potential trees (27 species), herb–subshrub (17), climbers (20), and epiphytes (15). Species richness increased significantly with the size of woody islands, corroborating one of the basic premises of Theory of Island Biogeography. Diversity and abundance of life-forms in the contrary were not significantly different along the different sizes. The comparison of all woody islands from the four study sites indicated a higher similarity within each site, suggesting regional variation in soil properties, past disturbances, or landscape contexts.