Soil characteristics are the most important factors influencing species distribution in alluvial forests. Here we evaluated species composition, diversity and structure of three forest strata and their relationship with soil characteristics in a fragment of alluvial forest in the Iguaçu River basin, Paraná state. We asked if forest structure and diversity can be explained by edaphic and hydrological factors. We evaluated structural variables and floristic composition of three forest strata: regeneration stratum (20 cm < height < 1.30 m; 80 subplots, 1 m×1 m), intermediate stratum (perimeter at breast height - pbh < 15 cm, height > 1.30 m; 20 subplots, 5 m×5 m) and upper stratum (pbh > 15 cm, 20 subplots, 10 m×10 m). In addition, we correlated species abundance with soil parameters in each subplot. The forest was characterized by a low diversity (Shannon's index: regeneration stratum = 2.36; intermediate stratum = 2.49; upper stratum = 1.59) and high floristic similarity among strata (Sørensen index > 0.65). The relationship of species spatial distribution and soil characteristics was distinct among strata: species distribution was correlated with soil water-table levels and organic matter content in the upper stratum and with soil water-table levels and aluminum concentration in the intermediate stratum. On the other hand no significant correlation was verified in the regeneration stratum. Our results suggest that community structure and floristic composition in alluvial forests reflect different interactions during individual life cycles.
Araucaria forest; ombrophilous forest; regeneration stratum; soil nutrients; water table
