Diversity and Richness of the Herbaceous Assemblage on Urbanized and Non-urbanized Dunes on the Brazilian Amazonian Coast

Abstract The urbanization is a factor that directly affects the structure of vegetation, which makes it essential studies aimed at conserving the biodiversity of these environments. This study aimed to describe the structure of the vegetation and identify the predominant species in order to record the herbaceous composition in non-urbanized and urbanized dune areas, analyzing the diversity of and richness of the dunes of Maranhão Island. The study was conducted in six dunes in which were allocated 150 plots in non-urbanized and 150 plots in urbanized dunes. We counted all the herbs in each plot (1 m2), recording data on richness, diversity and vegetation cover. To evaluate the difference in the composition of the areas, the following tests were used: Shapiro-Wilk W test (data distribution), Student t test (species richness) and Hutcheson t test (diversity comparison). NMDS showed that the urbanized and non-urbanized dunes presented distinct species compositions and densities; ANOSIM and the INDVAL test revealed a significant correlation between dunes and plots. We recorded 3,643 individuals: of this total, 2,075 individuals in urbanized dunes and 1,568 individuals in non-urbanized dunes; we found 91 species, 59 genera and 27 families. Richness was higher in urbanized areas; however, non-urbanized areas showed greater diversity and uniformity. The floristic composition of the areas differed, according to the species indicator, showing 19 typical urbanized dune species and 9 non-urbanized dune species. The diversity of the herbaceous vegetation provide important data that can be used to guide research on conservation and management of dune areas.