Tree species structure from a semideciduous seasonal forest under flooding at Cruz Alta, Rio Grande do Sul

Abstract

This study aimed to analyze the structure of the tree component from a seasonal semideciduous forest frequently flooded by identifying the main species structuring such remnant. We sampled all individual living trees with PBH≥15 cm into 16 10x10 m sampling units and calculated absolute density, frequency and dominance parameters. We surveyed 224 individuals from 21 species, 20 genera and 15 botany families. The species Cupania vernalis Cambess., Sebastiania commersoniana (Baill.) L.B Smith & R.J Downs, Luehea divaricata Mart., Ocotea pulchella Mart. and Sebastiania brasiliensis Spreng. showed the highest density and frequency values. On the other hand, Parapiptadenia rigida (Benth.) Brenan showed low density and frequency values but taller well developed individuals, which confer to it high dominance. Related to diversity and evenness estimates, the Shannon (H) index was 2.16 nats. ind-1 and the Pieou (J) index was 0.71. The remnant showed low species richness probably due to the frequent flooding. Not withstanding, the occurrence of particular species as Pouteria salicifolia (Spreng.) Radlk. clearly indicate the conservation needs of such areas mainly due to the ecological role riparian forests play in that region.