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The Shenandoah National Park's lichens are odd, interesting and under siege Date published: 12/8/2008
By LAURA MOYER THORNTON GAP--A blast of snow whitened the Skyline Drive's Jewell Hollow Overlook one late fall day, covering the parking area and an old stacked-stone fence that deters visitors from tumbling down the mountain. It was not a great day for Shen- andoah National Park botanist Wendy Cass to show a visitor the 93 lichen species that grow on this old stone fence, a 1930s Civilian Conservation Corps treasure. But it was a fine day for the lichens themselves. These slow-growing organisms--a symbiotic partnership between fungi and algae--thrive in this high, exposed place and on other rock outcrops throughout the park. They take sustenance from sunlight and drink in moisture from rain and snow. Scouring winds don't budge them, and they're suited to altitude and cold. Many of the park's 471 known taxa of lichen are under siege not from the elements, but from the crunching thuds of hikers' feet. A recently completed three-year study of the national park's rock outcrops turned up finds to thrill the hearts of lichenologists: At least 11 lichen species never before noted in Virginia Two species never before found east of the Mississippi River One species believed to be new to North America Six species potentially new to science And at least 11 species at the very southern tip of their range--leftovers from the last ice age. These relics of a colder time cling here in tiny islands of habitat. If they were trampled, Cass said, they wouldn't be able to re-establish and would probably be replaced by opportunistic "weedy" lichens already prevalent in the park. The rock-outcrop study looked at all the related plants, animals and geologic and soil resources. Lichen originally were just a small part of the study. But early discoveries were so significant "we realized we should spend a little more time on it," Cass said. Professionals and volunteers looked at 50 sites to identify as many lichen species as they could. The lichens they found are of three general types: crustose, or growing into the rock itself; foliose, a flat, leaflike projection from a surface; and fruticose, or thin, fingerlike projections. A few species are spectacular to look at, with bright oranges, reds, yellows and greens forming intricate patterns. But most are so unobtrusive they wouldn't catch a hiker's eye. Pretty or not, lichens fill a natural niche. They colonize bare rock and secrete acid that over many millennia breaks down rock to help form soil. They're sensitive to pollution and thus are a natural indicator of air quality. And they provide food for insects and some small mammals. At her office in park headquarters near Luray, Cass showed a visitor a pre- served specimen of a foliose lichen. It's a fragile round plate hardly thicker than a piece of construction paper and about 2 inches in diameter. This type of lichen grows maybe a millimeter per year, Cass said, which means it took this particular piece about 40 years to form. "But one footstep will knock it off a rock," she said. Laura Moyer: 540/374-5417
Date published: 12/8/2008
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