BENNETT, JAMES P. Institute for Environmental Studies, University of Wisconsin, 504 Walnut St., Madison, WI 53705. - Algal layer thickness in Parmelia sulcata as an environmental indicator.
Samples of Parmelia sulcata from North American sites were
sectioned and the algal layer thickness measured to test for
differences from different national parks and other localities. Total
thallus thickness and algal layer thickness and their ratio varied
across the country, but the overall variability was low. Sites nearer
urban areas tended to have lower algal layer ratios, indicating that
the photobiont may be the more sensitive component to air pollution.
Differences were observed even though no discoloration or other signs
of stress were apparent.
Key words: air pollution, layer thickness, lichen, Parmelia sulcata, photobiont