Resumo Este estudo compreende as espécies de Loganiaceae ocorrendo sobre canga na Serra dos Carajás, estado do Pará, Brasil, incluindo descrições detalhadas, ilustrações e comentários morfológicos das espécies. Ao total, foram registradas quatro espécies, duas de Spigelia e duas de Strychnos: Spigelia anthelmia, de distribuição neotropical; Spigelia flemmingiana, que ocorre desde a região Sudeste do Brasil até as Guianas; Strychnos cogens com ocorrência na Amazônia brasileira, Venezuela e Guianas; e Strychnos mitscherlichii var. mitscherlichii, distribuída na Amazônia brasileira, Guianas, Venezuela, Colômbia, Equador, Peru e Bolívia.

Abstract The present study comprises species of Loganiaceae that occur on iron-stone (canga) substrate at the Serra dos Carajás, in the Brazilian state of Pará, including detailed descriptions, illustrations and comments on the morphology of the species. In total, four species were recorded in the study area, two of Spigelia and two of Strychnos: Spigelia anthelmia has Neotropical distribution; Spigelia flemmingiana, occurs from Southeastern Brazil to the Guianas; Strychnos cogens found in the Brazilian Amazon, Guianas and Venezuela; and Strychnos mitscherlichii var. mitscherlichii, found in the Brazilian Amazon, Guianas, Venezuela, Colombia, Ecuador, Peru and Bolivia.

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 fitossociológico foi realizado em uma área de vegetação campestre localizada na Serra do Sudeste, sul do Brasil, onde campos e florestas estão distribuídos em mosaico, buscando compreender padrões de diversidade em quatro comunidades. O manejo destes campos realizado pela população local é caracterizado por práticas de queimadas periódicas visando eliminar espécies lenhosas, retardando assim o processo de expansão florestal favorecido pelo clima atual. O número de parcelas por comunidade foi: campo rupestre (17), campo seco (33), campo úmido (15), campo brejoso (5). Diferentes totais de parcelas foram utilizados devido às condições naturais dessas comunidades, com uma alta cobertura de áreas de campo seco, seguido pelos campos rupestres, úmidos e brejosos. A análise de dados consistiu no cálculo de índices e parâmetros fitossociológicos e análises multivariadas exploratórias. Verificou-se que aproximadamente 15% dos 177 táxons registrados apresentaram maior dominância na composição da vegetação nas quatro comunidades, enquanto a maioria das espécies apresentou baixos valores de frequência e cobertura. Maiores índices de similaridade e diversidade foram encontrados entre campos secos e rupestres do que entre campos úmidos e brejosos. Conclui-se que o grande número de espécies raras e de frequência intermediária é determinante para os elevados índices de diversidade encontrados nestes campos.

A phytosociological survey was carried out in a study area located at Serra do Sudeste, southern Brazil, where forests and grasslands are distributed in a mosaic, seeking to unravel diversity patterns in four different grassland communities. Grassland management traditionally adopted by the local population is characterized by burning practices that aim to eliminate woody species, delaying the forest expansion process that is favored by the extant climate. The number of plots distributed per community was as follows: rocky grasslands (17), dry grasslands (33), moist grasslands (15) and marshy grasslands (5). Different numbers of plots were used due to the natural conditions of these communities, with highest cover for dry grasslands, followed by rocky, moist and marshy grasslands. Data analyses consisted of calculating community indexes and parameters and exploratory multivariate analysis. We verified that c. 15% of species among the 177 registered taxa were highly dominant in the constitution of the vegetation matrix in all communities, whereas most of the species showed low frequency and cover values. Rocky and dry grasslands showed higher similarity and diversity indexes than moist and marshy grasslands. We concluded that the large number of rare or intermediate-frequency species is decisive for the high diversity found in these grasslands.