by Patricia Robertson
If you’re out walking a forest trail next summer, you might see greater toad pelt or witch’s hair, along with figleaf pixie and pea-green crottle.
No, these aren’t the hallucinations of some aging prospector. They’re the common names of lichens. The boreal forest has hundreds of different species in a spectacular variety of forms and colours, yet we often overlook them.
Lichens, in fact, are an amazing life form. They’re actually two organisms living together – a fungus and an alga – and they’re able to live in some of the most extreme climates on the planet. “A lichen is a really cool organism that is a symbiotic relationship between a fungus and an alga,” says Yukon biologist Jennifer Staniforth.
Lichenologist Trevor Goward puts it this way: “A lichen is both an organism and an ecosystem at the same time. From one perspective it’s a fungus that’s discovered agriculture, while from another it’s an alga that’s discovered domesticity.
“Perhaps the most helpful way to think of a lichen is as a living fungal greenhouse, where algae are being farmed inside the body of the lichen.”
Worldwide there are upwards of 20,000 lichens. The Yukon Conservation Data Centre reports 410 confirmed species in the Yukon, with another 206 reported but unconfirmed. Goward suspects that there are probably over 1,000 in the territory.
Lichens have also been around for a long time – far longer than many other life forms. “Lichens don’t fossilize very well; they just rot,” says Goward. “But the oldest known lichen-like imprint is about 400 million years old. There’s a school of thought that says lichens were the first macroscopic land organisms in the world.”
Lichens are adapted to conditions that the partners could not withstand individually and that most other organisms can’t withstand. Goward calls them “the biological chinking – they grow in places where nothing else can grow.” Staniforth adds that “they can withstand cold, they can withstand drought – there are even intertidal lichens.” The proportion of lichens to other species goes up as you move northward because lichens can thrive in such extreme habitats. “They are nature’s pioneers, being the first to colonize an area,” says Staniforth.
Where can you find lichens? Almost anywhere you look in the Yukon. They can grow on the soil, dead wood, rocks, or tree trunks. Xanthoria elegans, for example, often grows in rocky outcrops below birds’ nests because it likes the bird dung. This bright-orange lichen, also known as elegant sunburst, is a good indicator of raptor nests in rocky areas.
Lichens can be divided into three forms: crustose, or crust-like; foliose, or leaf-like; and fruticose, or stalked. Fair Isle lichen is a crustose lichen that grows on rocks in a pattern of circular coloured bands, like the traditional Fair Isle sweaters.
Plated rock tripe (Umbilicaria muelenbergii) is a black foliose lichen with a series of “plates” on its lower surface, while madame pixie (Cladonia coccifera) is an example of fruticose lichen. It consists of tiny greenish stalked cups with a red fruiting body that produces spores. The various pixie cup lichens all belong to this genus or type.
There are also species unique to Beringia, including a tumbleweed-like lichen called Masonhalia richardsonii that rolls around the tundra.
Letharia vulpina, or wolf lichen, is the only known poisonous lichen in the Yukon, growing on twigs. It’s toxic because of the vulpinic acid it contains, which is poisonous to all meat-eaters and has been used as a wolf poison in Scandinavia. This lichen, like a number of others, has also been used to produce a bright yellow dye.
Lichens are the most powerful bio-indicators in existence – that is, they are the first visible organisms to respond to environmental change. That’s because they grow in very specific habitats where there is a balance for the two partners. “They read the landscape at a very, very fine scale,” says Goward. “I like to think of them as the second hand on the clock of ecological change.”
Many animals, including caribou – which would not exist without lichen – depend on lichens in one way or another. In the Yukon, woodland caribou mainly eat Cladonia rangiferina, known as grey reindeer lichen or “caribou moss” (although it’s not a moss). It’s a light-coloured, fruticose lichen found mainly in the boreal forest and is extremely cold-hardy.
“The Cladonia lichens are very high in carbohydrates and thus energy,” says Yukon caribou biologist Troy Hegel. “However, they’re also very low in protein, so caribou will also eat other foods such as evergreen shrubs and horsetails in the winter.”
Caribou possess a special four-chambered stomach, including a first stomach called a rumen. This rumen contains special intestinal bacteria that can break down lichens. Other ungulates, such as many of the deer family, also eat lichens. Smaller mammals such as flying squirrels and the red-back vole eat lichen as well.
Squirrels and birds will also use lichen for nest-building, such as the various hanging Bryoria or horsehair lichens. The Rufus Hummingbird uses hammered crottle (Parmelia sulcata) to camouflage the outside of its nest.
Like many lichens, the Cladonia lichens are slow growing (3 to 5 millimetres per year) and may take decades to return if overgrazed, burned, or trampled. After a forest fire, it takes over 100 years to regain a forest lichen community. So tread lightly the next time you’re hiking through the bush. Those lichens beneath your feet are pretty special.
This column is co-ordinated by the Yukon Research Centre (YRC) at Yukon College with major financial support from Environment Yukon and YRC. The articles are archived at www.yukoncollege.yk.ca/research/publications/newsletters