Structural Arrangement and Diversity of Herbaceous Flora of the Dunes of Caúra Beach, São José de Ribamar, Maranhão State

Abstract

Although the dunes are considered permanent preservation areas, anthropogenic factors have been altering the vegetation structure. Thus, research on the structural arrangement of herbaceous vegetation is important to understand the organization and distribution of species in this and other contexts. This paper aim to carry out a phytosociological analysis of the herbaceous flora of the dunes of praia do Caúra (municipality of São José do Ribamar, Maranhão state). For sampling, 10 transects of 50 m were traced, parallel to each other at a distance of 10 m, totaling 50 plots. Individuals that did not show lignification throughout their entire length were considered herbs, including rhizomatous or stoloniferous species. The structural parameters calculated were relative frequency, relative coverage, importance value, Shannon-Wiener diversity index (H') and Pielou equability (J'). A total of 643 individuals were sampled, belonging to 37 species distributed in 19 families, of which Fabaceae (10 species) and Cyperaceae (6 spp.) were the most representative. The highest values of frequency, vegetation cover and importance value were recorded for Paspalum maritimum  (51.66%), Chamaecrista hispidula (18%), Centrosema brasilianum  (16.84%), Alternanthera brasiliana  (12.58%), and Sporobolus virginicus  (11.43%). The Shannon-Wiener diversity index was 2.37 nats/ind and the equability was 0.62. These values are considered high when compared to different dune areas, highlighting the importance of conserving these environments on the coast of Maranhão.