Diversidade vegetal em restingas do litoral setentrional brasileiro

Abstract

Environmental heterogeneity is considered one of the main factors that act on changes in species composition patterns and may be related to climatic, edaphic and topographic characteristics. Species distribution can also be influenced by dispersal mechanisms, biotic interactions, and historical reasons, thus showing that different factors act as filters at different spatial scales and interact to result in the composition of an ecological community. Climate variation and habitat structure are proposed to characterize the areas of ecological tension between the Amazon and Cerrado biomes, providing the formation of different physiognomies. Among these areas of ecological tension, the restinga vegetation of Maranhão is limited to a transitional ecosystem, as they present vegetation of the surrounding biomes, covering narrow strips of the coastal zone of soils of the quaternary period of marine origin. The state of Maranhão is in a unique geographical position, which characterizes it in the ecotonal zone for presenting vegetation of the Amazon Forest and Cerrado biomes. The present study aimed to verify if there is an influence of the adjacent biomes of restinga vegetation of Maranhão as well as if the effects of climatic variables (precipitation and temperature) and spatial variable are related to the vegetation distribution. To test the hypotheses, a database with floristic studies of restinga vegetation of the Amazonian coast of Maranhão and Pará, restinga vegetation of the northern coast of Ceará and Piauí and of the Amazon and Cerrado biomes covering 23 areas was performed. A canonical analysis of principal coordinates was performed to measure the distance in species similarity between different areas and to evaluate the influence of precipitation and temperature climate variables and spatial variable. Subsequently, a variance partition analysis was performed, generating a Venn diagram to graphically present the individual effects of spatial variables on species composition. It was observed that the temperature and precipitation variables and the spatial variable did not influence the restinga vegetation of Maranhão, although the Venn diagram shows that the climatic variables presented higher value when acting together, instead of isolated. Therefore, although restinga vegetation of Maranhão is between the Amazon and Cerrado biomes, the analysis showed that their floristic composition was not influenced by the flora of these biomes, being explained by the theory of neutrality where dispersion limitation is a major factor independent of environmental differences.