Levantamento florístico do Parque Nacional dos Lençóis Maranhenses, Barreirinhas, MA.

Abstract

The Maranhão shows vegetation composed of floristic elements belonging to different phytogeographic domains: Amazon, Cerrado and Caatinga. The region of the Lençóis Maranhenses is located in the transition zone between these three biomes, forming a mosaic of ecosystems considered unique in the country, covering an area composed by dunes that move toward the interior of the continent for about 50 km. With a veiy varied vegetation, the region of the National Park of Lençóis Maranhenses (PNLM) is stül little known floristically. In view of the Maranhão still represents a gap in knowledge of Brazilian flora and that for the National Park of Lençóis Maranhenses no broader work of flora, this project aims to contribute to the knowledge of the species of the flora of the park, sampling the area that corresponds to the city of Barreirinhas, As well as subsidising the increment of botanical data (labels, lists of species, specimens in herbaria), both to the Maranhão as well as for Brazil. Collections were made between October 2016 and Augnst 2017, together with the analysis of the material deposited in HERBARIA MG, IAN e MAR. The identification of the species and the classification of forms of life followed the usual methodology in floristic studies, which were listed 288 species, 188 genus and 73 families. Of this total, 71 species are presented as new occurrences for the Maranhão, and families with greater number of species are Poaceae and Cyperaceae, Fabaceae, Rubiaceae, Eriocaulaceae, Myrtaceae, Apocynaceae, Polygalaceae, Xyridaceae and Euphorbiaceae. Bacopa cochlearia (Huber) L.B.SM., is in danger, and Gomphrena chrestoides C.C. Towns, almost threatened, according to the National Center for the conservation of flora. The floristic composition of the area under study was compared with other floristic surveys conducted in areas of restinga; two in Pará, Maranhão and Piauí. The analysis revealed low floristic similarity between the selected areas, indicating that there is a relationship between the geographical location of the areas and the formation of the vegetal groups. The results presented here are part of the richness and importance of PNLM, contributing directly to the knowledge of the flora of Maranhão. It also highlights the need for further efforts in the knowledge of the flora of PNLM, broadening the sample for the other municipalities that the park covers.