Epiphytic lichen communities are well established indicators of urban air pollution and habitat alteration. In regions experiencing urban development, a long-term decline in species diversity of epiphytic lichen, particularly species sensitive to sulfur dioxide, nitrogen oxides, and particulate matter, may be linked to increasing transportation and industry. To investigate the application of epiphytic lichens as indicators of air pollution and habitat alteration in southwestern Pennsylvania, USA, we measured species diversity and lichen health along a landscape gradient, which included 12 plots within multiple urban sites in the City of Pittsburgh and 12 plots within two rural sites outside of downtown Pittsburgh’s airshed. Additionally, we transplanted lichens from rural sites to locations with contrasting air quality to evaluate differences in biomass growth rates across the landscape gradient. To further examine the impact of microhabitat on lichen health, bark pH was measured at all plots and compared to the health of epiphytic lichens. Tree bark provides the substrate for epiphytic lichen species, in addition to being a simple and sensitive indicator of air pollution.
We found that urban and rural regions show contrasting communities of epiphytic lichen corresponding to air pollution and habitat alteration. More than twenty lichen species were identified among all sample plots, with the most common species being Flavoparmelia caperata and Parmelia squarrosa. Anaptychia palmulata and Parmelia squarrosa, two sensitive species to air pollution, were more robust and abundant at rural sites. Early results suggest that species richness of lichens can be used as an indicator of air quality. We also found that the distribution of lichens within any given wooded park is affected by habitat structure, such as canopy cover and moisture content. Lichens contribute to biodiversity, so that tracking changes in these communities can be an early indicator of more serious changes across the larger ecosystem.