Structure of the arboreal community of a riparian forest in southernmost Brazil

The aim of this study was to understand the structure of the arboreal community from riparian wood remainders at the Taquari river, in the Taquari-Antas river drainage basin, Rio Grande do Sul, Brazil. 263 sampling units (SUs) of 100 m2 along transects parallel to the river were established. Height and girth measurements were taken at every SU for individuals with a breast-height girth ≥ 20 cm. Absolute and relative parameters for frequency, density, and dominance were defined, as well as the importance value index (IVI). The diversity was estimated by the Shannon (H’) and Pielou equitability (J) indexes. The similarity between fragments was assessed by clustering and principal coordinates analysis, considering the IVI and species abundance values, respectively. Were sampled 3.995 individuals, 112 species, and 39 botanical families were sampled. The absolute density was estimated at 1483 ind/ha. As to IVI, Luehea divaricata Mart. and Zucc. came first, followed by Terminalia australis Cambess. and Lonchocarpus nitidus (Vogel) Benth. Morus nigra L., an exotic invasive species, occurred in all remainders and ranked ninth in terms of IVI. The diversity was measured at H’: 3.78 nats/ind and J: 0.80. The fragments that are geographically closer and suffer direct influence from flooding present a greater similarity among each other. Despite the presence of exotic species, the riparian woodland remainders at Taquari river present high rates of floristic diversity, revealing the need for the adoption of urgent measures for their preservation. The differences between the remainders show that the knowledge of nearby remainders is required for the implementation of rescue projects.