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Lichens--Deterioration; Vegetation surveys; Plants--Effect of air pollution on


A survey of three common epiphytic species of foliose lichens was conducted about a coal-fired steam electric station in North-central Minnesota during the summer of 1977 to assess general lichen health on a gradient basis from a point-source of air pollution. Health, as judged by abnormal form and color, of nearly 3,500 lichen specimens was recorded in 35 vegetation survey plots from a total of 291 trees. Lichen discoloration and degeneration decreased with increased distance from the power plant, and little deterioration was observed beyond 3 miles. Within the plant vicinity, lichen damage was noted on tree boles facing the plant which were impacted with fly ash. Maximum damage of lichens followed the pattern of prevailing winds (NW-SE). Sulfur analysis of lichen thalli was not correlated with visible damage distribution tended to decrease at the most distant plots (30 mi. from source).

Considering the sensitivity of foliose lichens to declining air quality (especially S02 pollution), pollution sources in the rural environment are bound to affect lichen communities, as this study indicates. More sophisticated lichen surveys coupled with future monitoring of pollution would be a valuable contribution to the general environmental impact assessment of coal-fired electrical energy production.

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