Brazilian Decidual Tropical Forest enclaves: floristic, structural and environmental variations

Abstract

Several theories have been proposed to explain the raised richness and diversity of species in native tropical forests, with an emphasis on those that invoke the niche characteristics. In the present study, we sample the woody vegetation in four enclaves of Deciduous Forests and investigate whether environmental variables can explain the floristic and structural differences among the sampled fragments. The studied areas are located the “Cerrado” biome core zone and in “Cerrado”–Atlantic Forest and “Cerrado–Caatinga” transition zones. The woody vegetation (diameter at breast height—DBH ≥ 5 cm) was sampled in 100 plots of 20 × 20 m, 25 plots in each enclaves. The investigated environmental variables were chemical and textural properties of the soil, rockiness, declivity and altitude. We found significant differences for the floristic variables (richness, diversity), among all the environmental variables, as well as for the density, height and for the DBH first class. We noticed strong influence of the environmental variables, and the nutrients availability, texture, soil acidity and the land relief are the most responsible for the floristic-cultural difference. We propose that the gradient existence of rainfall has influenced the edaphic characteristics, creating variations in the habitats, which may have favored the arrival and establishment of different species in each study area and the distinctive development of the woody vegetation at the enclaves to the Deciduous Forest.