Australia: The Land Where Time Began

A biography of the Australian continent 

Lichen are a symbiosis between a fungus and algae and/or cyanobacteria. They are long-lived and slow-growing. Lichens are formed when the fungal hyphae grow to form a tightly interwoven mass. Fungi are non-photosynthetic, so they require a photosynthesising organism, algae and/or cyanobacteria that can photosynthesise, to allow them to survive in symbiosis. The tough fungal mat provides a protective, evaporation resistant, environment that maintains the conditions necessary for the survival of the photosynthetic organisms, and chemically degrades the substrate to access the minerals necessary for both partners. The photosynthesisers provide the fungi with the products of photosynthesis.

Lichens and very resistant to climatic extremes, being capable of surviving long droughts in an air dried state. They are much more sensitive to heat when wet, so their distribution is limited by the time of year when rain is more likely.

The body of the lichen can take a number of forms.

Crustose Lichen

About 75 % of lichens known from Australia are of this type. In the arid zone of Australia lichens are almost all of this type, some being of the scaly lichen type. They bind tightly to the soil, having no lower surface. Some have the appearance of large bird droppings many centimetres across.

Scaly lichen

These have a thicker thallus than crustose lichen, and may have a root-like structure that attaches them to the soil.

Foliaceous Lichen

Sources & Further reading

• Mary E. White, Earth Alive, From Microbes to a Living Planet, Rosenberg Publishing Pty. Ltd., 2003

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Lichens