Abiotic effects on the cover and richness of corticolous lichens on araucaria angustifolia trunks

Abstract

Lichens play a key role in natural ecosystems, as they can function as primary producers, recycle minerals and fix nitrogen. Despite their environmental importance, little is known about lichen ecology in Brazil, and especially about how abiotic factors may influence their spatial distribution. In this study, we aimed to verify how the cover and richness of corticolous lichens on Araucaria angustifolia trunks vary between two different habitats (Forest and Grassland). The photoquadrat sampling method was applied to A. angustifolia trunks. The Coral Point Count software with Excel extensions (CPCe) was used to analyze photographs for lichen cover and richness. Additionally, a redundancy analysis was conducted to estimate how five abiotic and two biotic variables affected the spatial distribution of lichens. Twenty-five morphospecies were identified, none of them occurring exclusively in the Grassland habitat. Canopy openness, air humidity and tree trunk rugosity were important parameters influencing lichen distribution; therefore, spatial segregation of growth forms can be explained by environmental selectivity. Foliose lichens require more air humidity, which explains their predominance in the Forest habitat. Canopy openness in Grassland habitat favors fruticose lichens, which depend on factors such as wind for reproduction.