Lichen Recolonization Following Air Quality Improvement

Abstract

Air quality improvement near a coal-fired power plant led to recol- onization of Parmelia caperata (L.) Ach. in a pollution-induced void area. Recol- onization was first observed about four years after pollution abatement. Least- affected sites, i.e. near the edge of the original void, were first to recover while most-affected sites were slowest to recover. After eight years of improved air quality, the distribution of P. caperata has returned to near normal. Lichen bio- monitoring is useful not only to detect the effects of poor air quality but to docu- ment air quality improvement as well. There are numerous reports detailing the depauperate condition of lichens in polluted environments (Ferry et al. 1973). However, reports of lichen recovery following pollution abatement are almost nonexistent. This could be because repeating lichen work in a known area does not have the research appeal of new studies in an unknown area. It might also be because lichen recolonization is a relatively slow process. Henderson-Sellers and Sea- ward (1979) have followed the progress of Lecanora muralis (Schreb.) Rabenh. in an improved environment. They found a lag time of about five years before air quality im- provement was reflected by improved lichen distribution. Changes in fuels and industrial technology to meet strict emission standards have led to decreased air pollution levels in many areas. Information on lichen recolonization is valuable for interpreting lichen studies in those areas where pollution levels have decreased.