Lichen Recovery Follows Air Quality Improvement

Abstract

Air pollution has eliminated sensitive lichen species around many cities, industrial areas, and point emission sources. There is extensive literature documenting the decline of lichens in such areas and their use as bioindicators of air quality (Ferry et al. 1973). However, reports of lichen recovery following pollution abatement are virtually nonexistent. Changes in fuels and industrial technology to meet strict air quality standards have led to decreased pollution levels in many areas. Information on lichen recolonization is valuable for interpreting lichen studies in such areas. Lichens were first surveyed around Muskingum River Power Plant, Morgan County, OH, in 1973 (Showman 1975). I visited a total of 86 sites and recorded the lichen flora of each. Mapping revealed well defined void areas in the distributions of two common lichen species, Parmelia caperata (L.) Ach. and Parmelia rudecta Ach. The P. caperata void consisted of a discrete group of 19 sites extending to about 10 km from the power plant and covering an area of about 90 km2. The P. rudecta void was somewhat smaller, indicating that this species is less sensitive to power plant emissions. Near the edges of the voids I found relatively narrow struggle zones of injured lichens. Some other lichen species were also absent from the voids but their naturally low frequency prevented their use as bioindicators. The effect on lichen distribution was thought to be the result of the Muskingum River Plant contribution to sulfur dioxide levels in the area prior to 1972. In 1969 a major construction project began at the plant to install air pollution control equipment. The project was completed in 1972. Henderson-Sellers and Seaward (1979) consider monitoring of ameliorating environments to be best accomplished by the detailed investigation of a single lichen species. In the Muskingum River Plant area, particular attention was paid to the SO2sensitive species, Parmelia caperata. The area of study remained the same from 1973 through 1980. Of the original 86