Looking at Lichens

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Published on: Oct. 2, 1998

Last revision: Nov. 2, 2010

shaped lichen called a rock tripe is often fried and eaten.

Many lichens are common throughout Missouri, and a few are so distinctive or colorful that they are noticed by those who regularly go outdoors. Even though they often cover tree trunks, lichens are not tree parasites and do not damage trees. Lichens play a critical role in mineral nutrient cycling in many forests. Certain lichens are even capable of using, or "fixing," atmospheric nitrogen-an unusual trait shared only by a few plants, such as legumes.

We are just beginning to understand the diversity and importance of lichens in our natural systems. The Conservation Department, in conjunction with researchers from The Nature Conservancy and the Missouri Botanical Garden, is studying the lichens of Ozark woodlands as part of its Missouri Ozark Forest Ecosystem Project (MOFEP). This and other ongoing work on Missouri lichens has resulted in the discovery of several species new to science, including two that have been named after the state of Missouri.

You can identify three general types of lichens by their shape and appearance. Lichens with a well-developed, three-dimensional growth form, often looking like miniature trees or columns, are called fruticose lichens. The best known local examples of fruticose lichens are British soldiers, old man's beard and reindeer lichen. Fruticose lichens are often the first to disappear when a natural habitat is disrupted.

Probably the most common type of lichen in Missouri is the foliose lichen. These are flat, typically green or gray lichens that can be abundant on trees and rocks, especially in the Ozarks. These lichens come in a wide range of sizes, with some species less than 1/4-inch wide and others that are more than 10 inches wide.

Crustose lichens are the most diverse and least noticed group of lichens in Missouri. Just as their name implies, crustose lichens often look like a thin crust on rocks, soil, trees, fenceposts, shingles and old, rusted iron on bridges. Some crustose lichens even grow inside rocks, occupying the microscopic spaces between rock crystals.

Most crustose lichens are small and drab and require a microscope for identification. Few have common names, although the bright orange fencepost lichen (Caloplaca microphyllina) is an exception that provides a splash of winter color on weathered eastern red cedar and Osage orange posts in prairie and farm areas. A few types of crustose lichens are among our most adaptable species and even thrive on concrete in downtown St. Louis and Kansas City.

Important yet tiny, colorful but often overlooked, lichens play an unusual role in our environment and in human consciousness. We seldom notice them, yet our landscape would seem less rich and varied without them, and many plants and animals indirectly depend upon them in our natural systems.

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