ON EARTH ARE LICHENS?
July 7, 2013
to get children outdoors to look for a life form that doesn't bite,
sting, or pinch, and that they are sure to find? At a recent family
reunion in northern Alabama, every child brought back a sample. Most
were gray or green. Some were yellow, red, or orange. Some were on dead
tree limbs, others on rocks, and one was found on the wall of a building.
children away from cell phones and computer games and they quickly learn
to appreciate nature in all its myriad forms. The organism in question
is one that any child can find - in the backyard, at a park, or on an
old brick. I never get tired of my grandchildren saying "look at
the lichens I found."
is lichen (pronounced lie-ken)? Although they look like a single organism,
lichens actually represent a complex relationship between fungi and
algae. The species live together in a permanent symbiotic partnership
in which each provides for the other, contributing to their joint survival
in special and essential ways. Like higher green plants, algae convert
sunlight into usable energy through photosynthesis, a process fungi
cannot perform. Fungi are able to absorb vital nutrients from the surface
they grow on. Hence, algae provide energy; fungi supply minerals. Ultimately,
both species benefit, resulting in a single living organism that is
far more complex than its superficial appearance reveals.
are easy to find. Oaks and other hardwoods have patches of greenish
gray lichens that may be spongy or flat and dry. Lichens are everywhere!
Pick up a dead limb and you will find lichens. Next time you see what
appears to be a bare cliff face or rock wall, take a closer look. You
will find lichens anchored into the rock itself. More than 17,000 species
of lichens have been described, most belonging to the fungus group that
includes the edible morel mushrooms.
occupy a variety of habitats worldwide. What might seem to be a fragile
life form may actually be one of the toughest organisms around. I remember
being impressed by an entire mat of lichens covering a rock wall in
the Mojave Desert where temperatures were well above 100 degrees F.
Reindeer moss is a type of lichen eaten by caribou in arctic regions.
The lichen carpet in some regions of tundra provides the major source
of food and nutrients for the big herbivores, which in turn are a primary
food source for wolves. Ironically, an awesome predator ultimately depends
on a food chain that begins with a combination of fungi and algae.
the otherwise durable lichens are believed to be highly sensitive to
some components of modern air pollution. They have been reported to
be intolerant of toxic materials such as sulfur dioxide, heavy metals,
and fluorine. Lichens have been proposed for use as ecological indicators
in areas with high air pollution from industrial sources. One report
noted a gradual increase in lichen abundance from the center to the
outskirts of an industrial area.
serve as a food source for many animals, besides caribou, including
moths, slugs, flying squirrels and mites. Hummingbirds, vireos and other
birds use lichens for nest material. Lichens are even used by humans
for dyes, antibiotic salves and perfumes. Litmus paper, which can determine
the acidity of a liquid, is made from a species of lichen. And the alpine
reindeer lichen is used to make tiny little trees for model railroad
us pay no attention to lichens, yet they are an important and fascinating
part of the living world in our yards, local parks, and woods. Look
for the pale greenish or gray coating, sometimes in little patches,
on tree trunks, large rock faces, or on the soil itself. These two completely
different, little-noted life forms can live in harmony together to make
another that is remarkably persistent and pervasive. This is a natural
wonder as fascinating as any you might see on television. And it's right
outside your door. That's another thing I'm trying to teach my grandkids.
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