A Humid Forest refuge in the interior of the brazilian Northeast: structure and alpha and beta diversities

Inside the Brazilian semi-arid region (Caatinga biome) there are vegetation refuges from other biomes that are present mainly at greater elevations in ancient geological formations such as Chapada do Araripe. This study aimed to understand the structure, diversity and floristic similarity of a fragment of humid forest in order to support conservation strategies for this community in Chapada do Araripe, southern Ceara (708m Alt.), an area of relevant ecological, cultural and scenic value. In 13 parcels of 25x25m (0.8 ha) all individuals with DBH >= 5cm were inventoried, observing total height. Floristic similarity was observed using the Jaccard method, comparing it with seven other areas in different regions of the Brazil. Sixty-six species were found distributed in 34 families, in a total of 1,544 individuals with DA=1,997.30 ind.ha-1 and AB =32,618 m2ha-1. Fabaceae (25.75%) and Myrtaceae (6%) had the highest number of species and Brosimum gaudichaudii had the highest IVI. The Shannon index (H') was 3.13 and the Pielou equability (J') was 0.75. The beta diversity, compared with other areas of humid forest (core and disjunct), was considered high and the statistics showed greater similarity with the area of the mesoregion of Pernambuco forest. The results allow the characterization of the area as a vegetational refuge of humid forest, corroborating the Refuge Theory and showing strong penetration of savanna species ("Cerradao", Cerrado, Caatinga/"Carrasco"), emphasizing the action of climatic impulses that occurred in the Quaternary and pointing to the need to conservation strategies due to accelerated anthropism.