Ferns and lycophytes as a tool to evaluate environmental dissimilarity in riparian forests in southern Brazil

Riparian forests are heterogeneity due to biological and abiotic variables that influence environmental dynamics. The aim of this study was to investigate the floristic and environmental dissimilarity in three riparian forest fragments. In a 250-m transect, ten plots of 5 × 5 m were drawn in each fragment, totaling 30 plots. Floristic inventories were conducted. Abiotic variables (soil moisture and canopy opening) were measured, and the environmental quality was evaluated through the Rapid Assessment Protocol of Habitat Quality (RAPHQ). A total of 25 species were recorded in 20 genera and 12 families following the asymptote tendency for each fragment. The fragments revealed high diversity, and most species were distributed in diverse genera (FI: 12 species in 10 genera; FII: 13/11; and FIII: 14/14). Only three species were present in all fragments. In general, at least 44% of the species were shared at two or more sites. Our results indicated floristic and community heterogeneity among the fragments analyzed (R = 0.621 global, P = 0.001). Our findings showed that in FI and FII, environmental variations, such as lower scores in RAPHQ and soil moisture, reflected in lower species coverage and more homogeneous plant distribution. In FIII, the same environmental variables resulted greater coverage of plants and a more heterogeneous and equitable distribution among the plots. These results demonstrate that ferns and lycophytes are important tools to evaluate environmental dissimilarity in riparian forests, reasserting the bioindicator potential of these plants.