Floristic and characterization of grasslands vegetation of a granite hill in Southern Brazil

Abstract

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floristic and vegetation study was carried out in the grassland formations at Morro São Pedro, Porto Alegre municipality, Rio Grande do Sul State, a granitic elevation area, so far poorly surveyed, that cradles important natural vegetation remnants of the region. After the study, which lasted from April 2005 to March 2009, we found 497 angiosperm species, distributed in four main grassland formation types: dry grassland, rocky grassland, humid grassland and wetlands. Among the species list three species are noteworthy: Alstroemeria albescens, a new species for the science, Lepuropethalon spathulatum, a new record for Southern Brazil, and Thrasyopsis juergensii, a new record for the Pampa biome. Based on our results and on support from other papers we concluded that ca. 65% of the grassland species present in the granitic hills of the region belong to seven main botanical families (Asteraceae, Poaceae, Fabaceae, Cyperaceae, Rubiaceae, Verbenaceae and Apiaceae). The species belonging to these families are also determining in the vegetation phytophysiognomical and structural composition, so that cespitous grasses predominate in the landscape, shaping a continuous gramineous layer. The grasslands at the granitic hills of the municipality have an insular present distribution, isolated in patches at hilltops, due to the presence of forests in the slopes. They show a high number of species that can be found in higher numbers in dry areas than in humid areas, and there is a gap in works concerning the characterization of humid grasslands and wetland formations inserted at hilltops. Despite the significant plant diversity of these grasslands, their representation in conservation units at the municipality is virtually inexistent.