Flora e ecologia de comunidades lenhosas de inselbergs na bacia do rio Itapemirim, Espírito Santo, Brasil

Abstract

The Atlantic Forest represents the most biodiverse biogeographic domains on the planet, where inselbergs stand out, which are rocky outcrops formed by granitic and/or gneissic rocks, prominent elements in the landscape. Due to limiting environmental conditions, these environments are home to highly specialized plant species with specific adaptations and characteristics, generating a flora with high levels of diversity and endemism, making them excellent places for scientific studies. Thus, the present study aimed to characterize the flora and evaluate the structural patterns of woody vegetation and its relationship with abiotic factors, in three granitic inselbergs in the Itapemirim River basin, Espírito Santo, Brazil. In the first chapter, we analyze the composition of the woody flora of the vegetation and scrube islands of three inselbergs that make up the Pedra das Andorinhas Complex (CPA) and its similarity with other 12 inselbergs studied in Brazil, through clustering and ordination analyses. Based on 20 field expeditions carried out between 2019 and 2020 and literature data, we recorded a total of 27 species, 25 genera and 16 families. The Fabaceae and Myrtaceae families, and the Eugenia genus were the richest in species. The predominant pollination and dispersal syndromes were entomophilia and zoochory. In addition, Ficus cyclophylla, Trigoniodendron spiritusanctense and Wunderlichia azulensis make up the national list of threatened species, and Pseudobombax aff petropolitanum, Tabebuia reticulata and Wunderlichia azulensis are endemic to inselbergs from the Atlantic Forest and Caatinga. As for the geographic distribution, the predominant species were endemic to the Atlantic Forest (33%) and species with wide geographic distribution among the Brazilian phytogeographic domains (30%). The CPA has more species in common with other submontane seasonal semideciduous forest inselbergs in southern Espírito Santo, as a function of geographic distance. For the second chapter, in the three inselbergs of the CPA, 12 plots of 20 x 20 m were allocated (four plots per inselberg), randomly distributed in areas of woody vegetation. All woody individuals that had DBH > 5 cm were included and the abiotic factors collected in each plot were: soil physicochemical properties, soil depth, slope and exposed area of rock. We found no differences in species composition/diversity between the three inselbergs. Overall, 275 woody individuals were counted, distributed in 20 species, 18 genera, 12 families. The richest families in terms of number of species were Fabaceae (five species) and Myrtaceae (three species). The average density of individuals was 573 ind. ha-1 and total basal area of 8,782 m² ha-1, and the species with the highest IVI values for all areas were Pilocarpus spicatus and Pseudobombax aff petropolitanum. Our results support the hypothesis that the physical properties of the inselberg (slope, soil depth and exposed rock area) play a relevant role in the structuring of woody vegetation, influencing the abundance, richness and diversity of species. This study offers the first contribution to the knowledge of the woody flora of granitic inselbergs in Espírito Santo.