Comunidades vegetais em quatro pães-de-açúcar no Estado do Rio de Janeiro

Abstract

Rock outcrops present peculiar flora, being unique habitats which might be considered a barrier for many species due to their environmental conditions. Studies contemplating this type of habitat can provide relevant information about the evolutionary process and distribution of the species which occur there. The aim of this research is to generate more information on ecology, floristic and conser-vation of plant communities of four pães-de-açúcar in Rio de Janeiro state: Maciço do Itaoca (Campos dos Goytacazes), Costão de Itacoatiara (Niterói), Morro dos Cabritos at Parque Natural Municipal da Prainha and Monumento Natural dos Morros da Urca e Pão de Açúcar (Rio de Janeiro). The results are presented in two sections, the first dealing with the floristic, structural and environmental relationships of this type of vegetation, and the second one dealing with the floristic and conservation status of the rupicolous flora in general of the four study areas. In the first section sampling was carried out by combining lines (transects) and plots. Thus, were distributed 72 plots (1m x 1m) over three lines of 50m in each area. In those plots the presence of each species, area coverage and height of each individual was checked. It was also verified the type of substrate and taken measures of declivity, soil and litter depth. By the end of the field work, a total of 288 plots were marked on those four areas. Cactaceae, Bromeliaceae, Orchidaceae and Asteraceae are among the most important families. The results show that, among the species noted with higher importance value, are those with most influence in shaping floristic groups evidenced by principal component analysis (PCA) for the four areas. A redundancy analysis (RDA) was performed and showed that the variables that seem to influence floristic composition are shaped by the dynamics of vegetation itself. Data about the biological spectrum and species diversity index are also presented in this section. In section 2 were compiled information of herbaria collections and material collected at field excursions, forming a general listing with 193 rupicolous species from the four areas. Floristic data are presented, as well as their geographical distribution. About the species, 28 species are restricted to the state of Rio de Janeiro and 68 are endemic to the Atlantic Forest. Among them, 26 are inserted into some category of endangerment. Major threats and impacts on vegetation in those areas were addressed in the context of conservation of the rupicolous flora found. The most significant are fire, mining and the opening of new access on slopes with abundant vegetation.