Biological invasion by Hovenia dulcis Thunb. in forest fragments in Upper-Uruguay Region, Brazil.
We aimed to characterize the floristic and structural composition of the tree component of an area contaminated by Hovenia dulcis Thunb., to determine the relationship of the distribution of the invasive species to the successional stage, and to verify the relationship between the presence of invasive species with patterns of diversity and community structure. The study was conducted in a riparian area of the water reservoir of Machadinho Hydreletric power plant, in SC state. The survey was conducted in 48 plots of 200 m2 each, arranged in eight block. Within plots, all trees with circumference at breast height (cbh) greater or equal to 15.7 cm were measured (cbh) and identified. The data were analyzed through the phytosociological descriptors, the biological invasion index (BII), diversity index, non-metric multidimensional scalling, permutational multivariate analysis of variance, analysis of indicator species, and the c-score index. A total of 66 species was sampled, with the highest relative importance value (IV) for Ocotea puberula (Rich.) Nees (10.79%). H. dulcis ranked in seventh position of IV (4.04%) and the BII was 0.47. The blocks were classified into intermediate and advanced successional groups, with floristic and structural differences (p=0.001) between them. H. dulcis was associated with areas with an earlier successional stage, with lower diversity and a community with no structure, in relation to segregation of species within plots. We conclude that the invasion by H. dulcis did not occur homogeneously in the area, being influenced by ecological characteristics of the resident community.