A Comparison of Cover and Distribution of Corticolous Macro-Epiphytes in Three Woodlots in and North of Columbus, Ohio

Three woodlots, one urban, one suburban, and one rural, were studied for cover and frequency of corticolous lichens and bryophytes. Epiphyte cover was measured by fitting aluminum foil over the epiphyte, cutting and weighing the foil. Lichens less than 1 cm in diameter were assumed circular and the diameter measured. Cover and presence were noted only within a cylindrical quadrat 1.3 to 1.6 m high. Trees were chosen by the random pairs method (10 pairs/site). The epiphytes found were the lichens Physcia millegrana, Physcia orbicularis, Parmelia rudecta, Parmelia caperata, and Lepraria sp. and the moss Leskea gracilescens. Only one species was found at the urban site, P. oribuclaris. P. orbicularis, P. millegrana, and L. gracilescens were found at the suburban site. All 6 species were found at the rural site. Percent cover and percent frequency increased from the urban, to suburban, to rural sites for all species except P. millegrana, which was greatest at the suburban site. The probable cause of these differences in cover and frequency of macro-epiphytes is the greater concentration of atmospheric pollution, probably sulfur dioxide, in and near the city. OHIO J. SCI. 77(8): 146, 1977 Epiphytic corticolous (bark-inhabiting) lichens and mosses are very sensitive to atmospheric pollution and are generally absent or reduced around pollution centers such as cities and factories. Laboratory and field studies have implicated sulfur dioxide (SO2) as a major cause of this paucity of epiphytes, although other pollutants are probably involved as well (LeBlanc and Rao 1975). The impact of the urban environment on lichen communities has usually been studied by mapping the distribution of various species of corticolous epiphytes within the urban area. Cover and frequency of occurrance were used by Stephenson and Merriam (1975) to study the effect of urban pollution on lichen communities in woodlots in Ottawa, Canada. My study compares the cover, frequency, and presence of corticolous macro-epiphytes in three wooded lots to determine if Columbus, Ohio has a similar pattern of reduction of macro-epiphytes near its urban centers. 'Manuscript received December 28, 1976 and in revised form March 23, 1977 (#76-103). METHODS AND MATERIALS Greater Columbus is located in central Ohio (latitude 40° 00' N, longitude 83° 01' W) and has a population estimated to be 920,900 (Columbus Chamber of Commerce 1976). Columbus' industries are generally small and are not concentrated in any one area. The prevailing winds are S-SW at 8-9 mph, and the average annual rainfall is 940.1 mm. The reported pollution levels in Columbus are relatively low, especially sulfur dioxide, mainly because there are few major sulfur dioxideproducing industries in the area. One urban, one suburban, and one rural site was chosen for study solely on the basis of availability and location near (within 200 m) the east bank of the Olentangy River. The urban site, Tuttle Park, is located north of the Ohio State University campus and 5.8 km from the intersection of Broad and High Streets (the approximate geographical center of Columbus). The wooded area is moderately disturbed by human activity, however, there is no evidence of mechanical removal of epiphytes. This site is approximately 1.2 km north of the University power plant. From 1937 to 1970 the power plant burned an average of 350-400 tons of Ohio coal per day (G. Hess 1976), a substantial past source of SO2 directly upwind from the site. The power plant did not have scrubbers to remove effluent SO2 but in 1970 it converted to natural gas and oil as the primary energy source. The University power plant is located 4.7 km from the intersection of Broad and High Streets.