Sheet - Some Types of Lichen
500 species of lichens live in the northern forests of North America.
Lichens are different from fungi like bread mold and mushrooms--they're
Lichens (pronounced Li'-kens) are a fungus that has captured
some algae. These two plants form a symbiotic relationship, that
is, each contributes something of value to the other.
algae photosynthesizes, making food from the sun's energy. The fungus
consumes some of the food produced by the algae and, as its part
of the deal, the fungus wraps its fungal threads around the algae,
acting as a house for it. The fungus also collects water from rains
or moisture in the air and makes this water available to the algae.
Some lichens are green and become brighter green when wet. These
lichen fungi have a green-algae partner. Other lichens are not green
and don't become bright green when wet. These lichen fungi have
a blue-green algae called cyanobacterium as their algal partner.
(Some lichens incorporate both green algae and blue-green algae.)
don't have roots so they don't get their nutrients from the soil.
Lichens don't usually feed on trees and deadfall like fungi such
as puffballs or polypores (shelf or bracket fungi). Lichens absorb
water quickly and efficiently from the air, allowing their algal
partners to make food from the sun's energy.
are a source of food for other creatures such as caribou.
very sensitive to air pollution and many die-out when air pollution
are very good at preparing a disturbed area for more advanced plant
species. Raw areas like the barren, rocky land that exists after
a glacier retreats or a volcano erupts will often be colonized first
called soredia or isidia may be carried considerable
distances by birds. Once deposited, the fungal part begins to develop.
If it succeeds in capturing wild algae then it may become a lichen.
Lichens in barren
areas help create soil by injecting enzymes into cracks in rocks
which help break down the rocks into smaller particles. Eventually
enough soil may be created to allow colonizing plants to become
established from wind-blown or animal-carried seeds.
have discovered that lichens are some of the earth's oldest living
things, sometimes living for hundreds or even thousands of years.
Knowing this, they have developed methods to use lichens to help
estimate the geologic age of rocks and regions.