Effect of Grazing on the Plant Community of a Southern Brazilian Swamp

ABSTRACT Swamps have high biological diversity and are the largest producers of biomass. However, such ecosystems are threatened by human activities. This study analyzes the plant community structure of two swamp sites, with and without grazing. A total of 200 sample units with 0.25 m2 were distributed every 13 m to determine diversity, the Importance Value Index (IVI), and coverage. Fifty species and 18 families were recorded. Luziola peruviana Juss. ex. JF Gmel had the highest IVI, accounting for 62.57% of the relative coverage in cattle-influenced sites. In the portions without cattle, Commelina diffusa Burm.f. had the highest IVI (24.33). The Shannon and Pielou indexes were 2.18 nats.ind.–1 and 0.56, respectively, decreasing to 1.62 nats.ind.–1 and 0.47 in grazing sites. There was less richness in the cattle grazing area, with a single species accounting for a high percentage of coverage, indicating the possible role of grazing on the plant community structure.