Structural characterization and conservation status of the herbaceous stratum at Praia de São Marcos dunes, Maranhão State, Brazil

ABSTRACT

The coastal dunes have been identified as one of the most degraded environments. On the Brazilian coast, they threat the "restinga" vegetation. The objective of this study was to describe the phytosociological structure of the herb layer of dune vegetation and assess the conservation status of the area on the Maranhão coast. The study was conducted at São Marcos Beach located in the northern portion of the Maranhão Island. For the phytosociological sampling, we used the plot's method (50 plots of 1 m²⁾, and analyzed the traditional phytosociological parameters of vegetation. Also, there were determined the life forms, phytogeographic distribution and conservation status of vegetation community on site. In the sample of 50 m² we found 35 species from which Paspalum maritimum, Paspalum ligulare, Cassytha filiformis, Chamaecrista hispidula and Euploca polyphylla showed the highest importance value. When calculated for the cover values, the Shannon diversity index (H') was 1.69 nats m^-² and it was 3.04 nats m^-² when calculated for the frequency values. The area showed predominance of chamaephytes and therophytes indicating an adaptive strategy of vegetation to withstand adverse weather conditions. The sampled ecosystem presented widely distributed species in the Brazilian biomes, being absent endemism. There were identified 14 impacts factors of which five hit more severely the restinga vegetation of the São Marcos Beach. Therefore, more studies are needed with a focus on conservation of dune ecosystems to prevent damage compromising the plant diversity of these areas.

Keywords:
Phytosociology; Restinga vegetation; Anthropization; Maranhão´s Coast