The floristic composition of forest fragments was surveyed including tree, arborescent and shrub species in forest fragments in the municipality of Pelotas, Rio Grande do Sul state, southernmost Brazil. Data was collected by the 'walking' method in 21 forest fragments with different conservation status. The vegetation studied was characterized by two phytophysiognomies: a forest landscape matrix (Sul-Riograndense Slopes) and a grassland (Coastal Plain). A total of 148 species distributed in 101 genera and 48 families were found. Myrtaceae, with 24 species was the richest family, with genera representative in number of species: Eugenia (7), Myrcia (3), Myrcianthes (3), and Myrceugenia (3). Other genera had four species each: Schinus (Anacardiaceae), Baccharis (Asteraceae) and Myrsine (Myrsinaceae). Fabaceae with only two species contributed little to tree richness, with the Inga genus absent in riverine areas. There were species with typically tropical geographic distribution range such as Genoma schottiana Mart (Arecaceae), Alchornea triplinervia (Spreng.) Müll.Arg (Euphorbiaceae) and Schefflera morototoni (Aubl.) Maguire, Steyerm. & Frodin (Araliaceae), and taxa with temperate affinity such as Azara uruguayensis (Speg.) Sleumer (Salicaceae) and Quillaja brasiliensis Mart (Quillajaceae). This shows a biogeographic ecotone area between Mata Atlantica stricto sensu and Pampa Biome. But biodiversity is considered to be high because of latitude and low temperatures during winter. Further studies are necessary to develop appropriate strategies of conservation, restoration and management of trees and forest resources.
trees; biodiversity; conservation; ecology
