Diversity and structure of the understory of two forest ecotones in Maranhão and the influence of the urban environment

Abstract Forest ecotones are floristically rich but anthropogenic disturbances can differentiate their vegetation structure. This study evaluated the understory diversity of urban and nonurban forests in Maranhão. It tested the hypotheses that the understory of the nonurban forest has greater diversity and richness and that the spatial distribution of these variables in the understory of the urban forest has weak spatial dependence. The study was conducted in the municipalities of São Luís (urban area) and São José de Ribamar (nonurban area). Thirty plots (25m²) were demarcated and the woody individuals up to 2 m tall were measured. All phytosociological parameters were calculated. The differences in richness, density, and diversity were analyzed between the areas with the Mann-Whitney test, non-metric multidimensional scaling, and Hutcheson t-test. To visualize the variation in richness and diversity of the vegetation, ordinary kriging was used. There was a difference in the floristic composition and density of each species in the two areas; the richness and diversity were significantly greater in the nonurban area. The species with the highest IVs were Faramea nitida , Myrcia amazonica, and Ephedranthus pisocarpus in the nonurban forest and Protium heptaphyllum , Randia armata , and Moquilea tomentosa in the urban forest. Both understories had high diversity compared to other Amazonian regions. However, weak spatial dependence was found in the urban area, suggesting high anthropogenic interference in the environment. It is noteworthy that the areas represent a parcel of original ecotone vegetation in Maranhão and effective actions are needed to restore and conserve its diversity.