Flora, distribuição e estrutura da vegetação das áreas úmidas de uma região savânica brasileira: implicações para a conservação da biodiversidade

Abstract

This study was conducted in order to investigate the flora of the veredas, a type of wetlands of the Cerrado Domain, in the state of Mato Grosso do Sul (MS), Central Brazil, to check the distribution of species in other Brazilian morphoclimatic domains, list the first occurrence for the state based on the Flora of Brazil checklist, to assess the structure of the vegetation in veredas with and without Mauritia flexuosa L.f. (Arecaceae) and to compare these structural parameters, coupled with environmental and spatial variables, in an attempt to investigate whether veredas without Mauritia flexuosa are similar to those protected by the CONAMA resolution (defined by the presence of Mauritia palmeries). The floristic survey was performed by compiling all available data of flora surveys of veredas of MS and, submitting all names to the database of Flora of Brazil checklist in order to validate them and to obtain information on the distribution of the species in other Brazilian phytogeographic domains, as well as the first record for the state. To describe the vegetation structure, we inventoried 12 veredas distributed throughout the state. In each area, we defined six 50 m transects and placed 1 m side frames at five meter intervalss. Sampling was carried out according to the Braun-Blanquet method , estimating the percentage coverage of species occurring in each frame. We then performed ordinations of the vegetation structural data using NMS (non-metric multidimensional scaling) as well asRDA (canonical redundancy analysis) on the occureence matrices of floristic composition, and species frequency and coverage of. In order to asses species diversity, we prepared profiles using the Rényi series. The floristic survey revealed 1,056 species, distributed into 130 families and 444 genera. The most representative families were Poaceae, Asteraceae, Cyperaceae, Fabaceae, and Melastomataceae. The richest genera were: Rhynchospora, Paspalum, Hyptis, Utricularia and Ludwigia. We detected that 24.7% of the species listed here are firstly cited for Mato Grosso do Sul. A Cluster analysis revealed that the most species are shared with the Atlantic Forest Domain. In the study of vegetation structure, we sampled 249 species, 140 genera and 58 families. The richest families were Poaceae, Cyperaceae, Asteraceae, Rubiaceae and Melastomataceae. The richest genera were Utricularia, Rhynchospora, Eleocharis, Cyperus and Xyris. The filiform species Rhynchospora emaciata, Setaria paucifolia, Axonopus uninodis, Rhytachne rottboellioides, Andropogon virgatus, Paspalum dedeccae, Eriochrysis laxa, Anthaenantia lanata and Anthaenantiopsis trachystachya and the shrub Ludwigia nervosa were the species with highest importance values. Some species showed preference zones within the veredas while others occur throughout the areas. The Shannon Diversity Index was 3.89 and the Pielou evenness, 0.70. The diversity found is equivalent to other veredas in Brazil. We did not observe consistent patterns of distribution of species in areas with and without Mauritia flexuosa for Mato Grosso do Sul and the analysed variables suggest that there are no consistent parameter to consider them as distinct floras assemblages. We propose a thourough discussion in order to redefine vereda, thus including areas without M. flexuosa in legally protected areas.