Spatial distribution pattern of four fern species in three fragments of riparian forest in Cadeia River, RS, Brazil

Abstract

Spatial distribution patterns of four fern species, as well as the influence of topography, were described in three fragments of the Cadeia River riparian forest, under different levels of human impact in Santa Maria Herval, Rio Grande do Sul, Brazil. One hundred and twenty plots were selected, equally distributed in three fragments (FI, FII and FIII), in which we counted individuals of Anemia phyllitidis (L.) Sw., Ctenitis submarginalis (Langsd. & Fisch.) Ching, Dennstaedtia globulifera (Poir.) Hieron and Pteris deflexa Link. Aggregation indices were calculated for each species and then correlated with local topographic variables. The highest values of total abundance (467), mean (11.68) and maximum number of individuals (93) per plot were found in FII, for C. submarginalis. All species, irrespective of the fragment, leaned toward an aggregated pattern. C. submarginalis had the highest Ia value (3.37) in FI. This species showed average number of individuals per plot statistically equal, indicating a more homogeneous distribution for abundances in three areas. The Ia of species is weakly or moderately correlated whit topographic variables, suggesting that others factors such as soil and luminosity may be influencing the distribution of plants in riparian forest.