The lichen survey establishes a baseline for future studies of these important air quality indicators.
Lichen surveys may be repeated every 5-10 years to monitor changes in air quality, especially sulfur dioxide levels. The number of different species of lichens found (species richness) and the presence of two indicator species are studied to characterize the regional air quality impact on lichen populations.
This work represents the first systematic study of lichens at most state forests, however, lichen populations at Shawnee State Forest were also measured in 1984. Comparisons of the data collected at Shawnee Forest in 1984 and 1997 revealed stable, diverse lichen populations over the past 13 years, indicating that good air quality was stable in this region over the same period.
During the 1970’s, lichens were studied in areas of eastern Ohio where air quality was historically poor. Lichen populations were degenerating and key indicator species could not be found. Yellow Creek and Fernwood State Forests are located in this region and were included in our 1997 lichen survey.
Results of the survey show that lichen species richness is lower in this region than other areas of the state, but key indicator species are returning and lichens are recovering. This tells us that air quality in the region is improving. Lichen populations were healthy at all other state forests studied.
The objective of using lichens as bio-indicators is to qualitatively document the historical sulfur dioxide exposure of various forested locations in the state. It is important to note that the impact of air quality, and specifically sulfur dioxide, on Ohio forests is not clearly understood.