Phytosociological characterization of weed communities along a railway crossing the Atlantic Forest biome (Brazil)

Aims: To identify the floristic composition of weed communities present in Atlantic Forest environments. Study area: Stretch of 130 km of rail network located in coast and metropolitan regions of Sao Paulo, Brazil. Methods: The railway section was divided under influence of Forest and Mangrove ecosystems and Mangrove with human activity. For characterization and phytosociological study, 10 points of collection were made per environment, in triplicate (center and both sides of the main line), adding 30 sample units per area. For sampling a square of 0.4 m of side was randomly thrown at each point. The plants present within the square were counted and separated by species and family. The phytosociological indexes, density, frequency, similarity between areas and diversity were calculated. Results: 64 species were observed within 21 botanical families, with Poaceae and Asteraceae being the most representative. The forest area showed higher species richness (40% of species in this study), greater diversity or floristic heterogeneity (2.2 in the Shannon index). The species Pilea microphylla (Urticaceae) and Acalypha arvensis (Euphorbiaceae) had representativeness in all the ecological indexes raised in this study, with the highest relative density and frequency in total area (0.38 RDi and 12 Fri; 0.22 RDi and 13 Fri, respectively). High densities of Ageratum conyzoides (Asteraceae) were observed for forest area, Digitaria horizontalis (Poaceae) for the urban area, and Cyperus rotundus (Cyperaceae) in Mangrove. There was similarity in the floristic composition between the Mangrove and Urban Area areas (54%), which predicts a similarity among possible management tactics to be adopted. Conclusions: There was difference between invasive plant communities under the influence of different ecosystems. As the species and/or botany family of invasive plants on a site became known, the right weed control technique can be used, reducing effectively the impact of weeds on the railway activity, and the impact of chemical control on environment.