Physiognomy and floristics of a gallery-forest remnant along the Itapuã creek, Viamão, RS

Abstract

Although riparian forests are protected by the Código Florestal Brasileiro (Brazilian Forest Code) and have fundamental importance to the conservation of watercourses, human activities have been strongly damaging them. A floristic survey of the arboreal-shrubby species and a description of the vegetation located on the edges of Itapuã creek, Viamão, Rio Grande do Sul were carried out in order to evaluate the conservation status of the riparian vegetal communities and to provide a solution to the problems of environmental management in the region. The observation of the communities and collect of botanic material were done along continuous transects 30m far from each edge of the creek. The species were identified in the laboratory using bibliographic information, the ICN-UFRGS Herbarium and specialists. A list of arboreal-shrubby species was prepared containing their common names, families, habits and forest formations to which they belong. The riparian forest formations were classified in relation to the environmental conditions and by comparing their Sørensen similarity index. The total of species was 91, distributed within 39 families. The formations were classified as Psamophilic Forest of the Mouth, Psamophilic Forest of the Median-Lower Course and Hygrophilic Forest close to the springs. The high specific richness verified along the 13 km course of Itapuã Creek is due to the strong mouth-springs environmental gradient, which allows a great variety of niches. The 91 species recorded constitute about 37% of all native arboreal-shrubby species of the neighbor city (Porto Alegre). Some areas on the edges of the creek are damaged and show the environmental injury caused by the suppression of riparian forests.