Flood as a fine scale driver of both floristic and functional differentiation in a ripariansystem

Abstract

Flood forests are vegetation subject to seasonal floods. Situated in flood plains, they are systems under continuous changes due to the pulses of flooding, following the watercourse. Although these are singular ecosystems, there are little publications that report the floristic structure in floodplains, especially in Southeastern Brazil. This study aimed to characterize the composition, structure and diversity of the arboreal community in a flooding gradient, comparing them with the non-flood adjacent formations, at the mouth of Paracatu River, a tributary of São Francisco River, Minas Gerais, Brazil. For the structural survey of the arboreal community, we used the plot method, installed on both sides of Paracatu River. The individuals were identified at the species level. We sampled 1,276 individuals belonging to 85 species and 32 families. The Shannon Index (H`) regarding to the total sampling was of 3.40 nat.ind, with Pielou evenness index (J`) of 0.76. In terms of species importance, the six most important species comprised 46% of the total index of importance value. By means of similarity analysis, it was possible to verify the grouping of species along the ecounits, demonstrating the substitution of species along habitats, resulted of the temporal difference of the flooding in the environments. In conclusion, the flooding regimes, frequency and intensity determine the ecology of the river plains.