Few studies have adequately described the floristic and structural features of natural grasslands associated with shallow basalt soils in southern Brazil. This study was carried out on natural grazing land used for livestock production in the municipality of Santana do Livramento, in the Campanha region of the state of Rio Grande do Sul, Brazil. The aim of the study was to describe the floristic and structural diversity of the area. The floristic list obtained comprises 229 plant taxa from 40 botanical families, with a predominance of the families Poaceae (62), Asteraceae (28), Fabaceae (16) and Cyperaceae (12). The estimated diversity and evenness in the community were 3.00 and 0.874, respectively. Bare soil and rock outcrops accounted for 19.3% of the area, resulting in limited forage availability. Multivariate analysis revealed two well-defined groups among the sampling units. One group showed a high degree of internal aggregation, associated with deep soils, and was characterized by the presence of tussocks, whereas the other was less aggregate and was characterized by prostrate species growing on shallow soil. Ordination analysis indicated a gradient of moisture and of soil depth in the study area, resulting in different vegetation patterns. These patterns were analogous to the vegetation physiognomies described for Uruguayan grasslands. Overall, the grassland community studied is similar to others found throughout southern Brazil, although it harbors more winter forage species. In addition, the rare grass Paspalum indecorum Mez is locally dominant in some patches, behaving similarly to P. notatum Fl., a widespread grass that dominates extensive grassland areas in southern Brazil.

Um levantamento florístico e estrutural de uma comunidade de campo natural foi conduzido no Morro do Osso, um morro granítico em Porto Alegre, RS, Brasil. Os dados estruturais foram obtidos em 39 quadros de 1 m², dispostos em duas grandes áreas de campo. Uma queimada acidental ocorreu em uma das áreas, aproximadamente um ano antes do levantamento, propiciando a análise de diferenças entre os parâmetros dos dois sítios de amostragem. A lista florística contém 282 espécies e, no levantamento estrutural, foram encontradas 161 espécies. As famílias com maior valor de importância acumulado foram Poaceae, Asteraceae e Fabaceae. Os índices de diversidade e a equabilidade foram 4,51 nats ind-1 e 0,86, respectivamente. A análise de agrupamento identificou dois grupos nítidos, que coincidem com os locais atingidos ou não pelo fogo. Uma análise de similaridade entre os dados obtidos e dois outros conjuntos de dados de morros graníticos vizinhos resultou em 28% a 35% de similaridade, com uma equivalente distribuição de espécies por família e muitas espécies dominantes comuns, corroborando a noção de continuidade da flora ao longo dos morros graníticos no sul do Brasil.

A floristic and structural survey of a natural grassland community was conducted on Morro do Osso, a granitic hill in Porto Alegre, RS, Brazil. Structural data were surveyed in 39 one square meter plots placed over two major grassland areas. An accidental fire has occurred in one of the areas approximately one year prior to our survey, leading to further analysis of parameters differences between sites. The floristic list contains 282 species, whereas the structural survey has found 161 species. Families with highest accumulated importance values were Poaceae, Asteraceae and Fabaceae. The diversity and evenness indexes were 4.51 nats ind-1 and 0.86, respectively. Cluster analysis denoted two groups coinciding with the areas distinguished by the fire disturbance. A similarity analysis between our data and two other data sets from nearby granitic hills resulted in 28% to 35% similarity, with equivalent species-family distribution and many common dominant species, corroborating the concept of a continuous flora along the South Brazilian granitic hills.

Foi realizado o levantamento florístico das espécies de Cyperaceae do Centro de Pesquisa e Conservação da Natureza PróMata (CPCN Pró-Mata), Rio Grande do Sul. O local de estudo está situado no município de São Francisco de Paula, na região fisiográfica dos Campos de Cima da Serra. Foram efetuadas cinco expedições de coleta e encontradas 42 espécies, distribuídas em oito gêneros. São apresentadas a lista das espécies, chaves de identificação nos níveis genérico e específico e fotomicrografias em Microscopia Eletrônica de Varredura dos aquênios de cada espécie.

A floristic survey of Cyperaceae species at the Centro de Proteção e Conservação da Natureza Pró-Mata (CPCN Pró-Mata), Rio Grande do Sul was performed. The study area is located in São Francisco de Paula municipality, in the physiographic region of the Campos de Cima da Serra. In five collecting expeditions, 42 species were found at the study site, distributed on eight genera. A list of the species, analytical keys for genera and species, as well as scanning photomicrographs of the achenes are presented.