Ecological succession in two remnants of the Caatinga in the semi-arid tropics of Brazil

Abstract

This study was conducted in two areas of the Caatinga with altitudinal gradients (in a mountain range), in the microregion of the Cariri Oriental Paraibano. It had the goal of characterizing the stages of ecological succession of the plant communities based on the classification of species into ecological groups and comparatively analyzed the phytosociological structure of the two areas, which are influenced by different levels of anthropization. The tree-shrub flora (with diameter ≥ 3 cm and height ≥ 1 m) of the Serra Inácio Pereira was represented by 1043 individuals, 17 families and 42 species and in Serra do Monte by 1264 individuals, 13 families and 29 species. The Shannon diversity index was 2.790 and 2.313 nats.individual-1, respectively. Area I (Serra Inácio Pereira) had a higher diversity of families and species compared to Area II (Serra do Monte); the latter being more influenced by the process of anthropization. In Area I, the species of greatest ecological importance were Myracrodruon urundeuva Allem. and Sapium sp. In Area II, Caesalpinia pyramidalis Tul., Aspidosperma pyrifolium Mart. and Croton sonderianus Muell. Arg. were the species with the highest importance values (IV). Area I appeared to be in an intermediate stage of succession, where the pioneer species were dominant over the early secondary species, along with late secondary species with high IV. In Area II, 70% of the individuals were pioneer species, characterizing the vegetation as being in the process of regeneration. Area I had heterogeneous vegetation, exhibiting a healthy state of conservation. However, Area II appeared to be homogeneous, demonstrating that the level of disturbance accounted for the differences between the two areas in floristic composition, structural formation and, as a consequence, stage of ecological succession.