Understory epiphytic pteridophytes along altitudinal gradients on opposite slopes in the Atlantic Forest

Abstract

Gradual climatic changes caused by mountains’ altitudinal variation promote alterations in the structure of ecological communities. Environmental changes are also expected according to the slope’s position in relation to the sea. In this study, we aimed to compare epiphytic pteridophyte communities along altitudinal gradients on opposite slopes in a section of the Atlantic Forest. We sampled a total of 10 sites in the montane and upper montane zones from the eastern (facing the sea) and western (facing away from the sea) slopes. A total of 1,742 individuals from 62 epiphytic species were recorded. The slopes showed similar epiphytic abundances and richness. Species richness showed a tendency to decrease with an increase in altitude on the western slope, and abundance was higher at intermediate altitudes, with no altitudinal trend in dominance. Conversely, on the eastern slope, there was no clear altitudinal pattern in richness or abundance; however, dominance increased with an increase in altitude from 1,200 to 1,800 m. Species compositions differed among altitudinal zones and between slopes. The eastern slope had lower species richness and no clear altitudinal gradient, although it was better preserved than the western one. Thus, there are differences in the community structure of epiphytic pteridophytes from the forest understory due to altitudinal variation and slope orientation, and these findings corroborate our hypotheses.