Corticolous lichens as environmental indicators in urban areas in southern Brazil

Lichens are considered bioindicators and, as such, are widely used for air quality monitoring, especially in urban-industrial areas. The present paper proposes an evaluation of lichen communities in urban areas. The corticolous lichen community was assessed at 29 sampling stations in the city of Porto Alegre, in addition to a reference area located in the State Park in the city of Viamão, southern Brazil. The rubber band method was used for lichen mapping; three hundred host-trees were analyzed, at 11 different height levels. Lichens were evaluated in terms of composition, richness, cover and diversity, and sampling stations were classified based on the Index of Atmospheric Purity (IAP) complemented by the Environmental Classification Factor (ECF). The inclusion of ECF as a complement to the original IAP formula is proposed in the present study and not only richness and cover components are considered, but also data on the lichenized mycota composition (considering its different morphological forms). One hundred and thirty-one (131) taxa have been identified, out of which 13 specimens may be considered as indicators of urban areas, and the predominance of taxa belonging to the crustose and foliose morphological group was verified. The sampling stations were classified into five zones, ranging from lichen-free zones to optimal zones for lichen development. The use of lichen proved to be efficient to both evaluate air quality and identify alterations of urban microclimates. The application of an ECF-based correction factor is expected to complement the use of IAP, making it a more sensitive index, since an analysis of a multivaried information profile was deemed necessary, especially in regions where specimen diversity is higher.