The Next Page: The Secret World of Lichen
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At home on a host tree, Common Greenshield (Flavoparmelia Caperata) -
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It's that time of year when you head back out to the yard and assess what needs to be done.
Grass needs to be mowed, flower beds replanted -- and what's that green stuff on the tree trunks?
Don't worry about it. It's lichen.
Lichens don't harm trees. But, it's also not a plant. They are a symbiotic relationship between organisms in two different kingdoms. It's this relationship that has created a secret world beneath backyard canopies.
Lichens grow best on older, larger trees with ridges that they can cling to. But they're just hanging out there. They get their nutrients from the air and from photosynthesis.
How do I know so much about lichens? My husband, Matt, is an environmental science professor at Point Park and recently finished a study on the region's lichens. (If you want to read more about it, check out opdyke-environlab.com or listen to a podcast at carnegiesciencecenter.podomatic.com.)
If you broke off an edge of a lichen and took a close look under a microscope, you'd see bits of algae that had been trapped by fungus. The fungi have discovered agriculture. The algae provide food through photosynthesis for the fungi. When you separate the lichen out, algae does just fine, but the fungus will struggle to survive.
The coolest thing about lichens are their common names. In Pittsburgh's urban forests you'll find species like fluffy dust, candleflame and British soldiers.
Other names for lichen evoke delightful descriptions such as hammered shield, mealy rosette or pompon shadow. You never know when you might discover a smooth-footed powderhorn or stubby-stalked cladonia near a Monk's-hood. All of those are visible around Pittsburgh.
Some of the most flamboyant species in the U.S. can be seen in the temperate rain forests of Oregon and Washington. One might eye wooden signs serving as anchors for lichens. They grow much more robustly there than what you see in Schenley and Frick parks.
Lichens can be found in the extreme environments on Earth and as a whole make up one of the most abundant types of biological material. From the Antarctica to the arid desert, they often are nature's pioneers and help in creating soil. Rock tripe, for example, can survive without water for more than a year. In the boreal forest, lichens can help preserve soil moisture, add organic matter and trap seeds.
First Published May 8, 2011 12:00 am
