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Lichens

Rock encrusted with lichens

Lichens on granite Bald Rock NP NSW

Beautiful but often Overlooked

On a recent day trip to Binna Burra we stopped to enjoy the view of Mt Warning from Rosins Lookout near Beechmont and noticed that the tree trunks in the small park were encrusted with lichens – it was eye catching. (Location details below). Lichens have always attracted our attention, being drawn to their wide array of colours and forms from circular, flat, leaf-like arrangements to filamentous beard-like adornments hanging from tree branches. Lichen spotting has grown into an enjoyable part of our routine when out and about, and we collect photographs of the more spectacular examples.

Most lichens tend to fade into the background because of their flat growth pattern on the substrate (rocks, tree trunks, masonry, timber etc), but once your eye is in they are everywhere. To assist in lichen appreciation this blog lists some interesting lichen facts, provides technical information (shape, classification and reproduction) and uses photos to illustrate the various lichen forms.

Take some time to notice them and enjoy their different colours, structures and the substrates on which they grow. A deeper appreciation of lichen form, structure and fruiting bodies can be had using a simple X10 field hand lens and it is always a good idea to have one on your person when out and about. Relatively inexpensive hand lenses can be obtained from scientific suppliers such as Australian Entomological Supplies (model E275). If you want to encourage them on rocks in your garden the recommendations are that you apply some yogurt to the rock. It helps if the rock is not in full sun all day and that it is kept moist by occasionally misting it with water. We can’t give any guarantee of success since we have not tried this – but what the hell there’s nothing to lose so give it a go, but don’t go mad with the yogurt – just a few drops. Make lichen spotting part of you outdoor experience. It offers much enjoyment for little extra effort. Good hunting!

Out and About

Three well developed lichen colonies were observed recently –

  • on tree trunks at Rosins Lookout (1.5 klms back towards Nerang from the Beechmont roundabout Qld);
  • on palm trunks, Hoop Pine trunks and brick fences in Teemangum Street Currumbin Qld on the left just before the Currumbin Sanctuary roundabout going towards Currumbin; and
  • in the Main Range National Park, New South Wales. Filamentous lichens hanging in profusion from the branches of Antarctic Beech trees.

Lichen Facts

Although appearing innocuous lichens have an important ecological role in soil production and the absorption of carbon dioxide. They have an interesting, complex structure and can cope with harsh environments. Lichens are:

  • ancient life forms with the earliest recognisable fossils in the Lower Devonian (400 million years), but there are indications they could go back to the Cambrian (570 million years);
  • able to convert carbon dioxide into complex organic compounds such as sugars and release oxygen by photosynthesis;
  • first colonisers in new geological situations e.g. after volcanic eruptions.
  • an important early stage in the weathering of rocks and achieve this in two ways – by the small, filamentous root-like threads anchoring the lichens to their substrate forcing their way between the rock mineral interfaces and by producing chemicals that dissolve the rock minerals;
  • at the beginning of soil production process through rock weathering;
  • capable of surviving in localities with extremes of temperature, humidity and light by temporarily shutting down their metabolism;
  • found in any habitat from backyards to the desert and any zone from the poles to the equator.
  • are capable of capturing moisture from dew and fogs which aids their wide distribution;
  • found on a variety of substrates including wood, tree bark, rocks, leaves, masonry, and stone monuments in cemeteries;
  • the sources of chemicals used in dyes and natural medicines; and
  • ecologically important especially in the arctic tundra where they cover many thousands of square kilometres.
Lichens Blue Mountains

Lichens Blue Mountains

Lichen Structure and Classification

Structurally lichens are not a single organism, but the combination of two groups forming a mini-ecosystem –

  • a fungus (mycobiont) without chlorophyll; and
  • photobionts – algae with chlorophyll or cyanobacteria with photosynthetic pigments. The photobionts use light and carbon dioxide to manufacture complex carbohydrates (photosynthesis) and provide the colour in lichens. Photosynthesis also releases oxygen into the atmosphere.

The relationship between the fungus and the photobionts is thought to be symbiotic (each benefiting the other) – the fungus providing the minerals and the photobionts the complex carbohydrates. Some botanists believe that the relationship may be master and slave, with the photobionts the slaves.

The union of these two organisms produces a distinctively shaped structure that is different from either of its two components. Classification is based on the fungus since each lichen has a unique fungus. The photobionts have their own names and occur across a number of different lichens. Lichens are broadly grouped under three headings based on shape and habit –

Crustose – Crust-like closely adhering to the substrate and having diffuse edges. Shape more-or-less circular. There are some crustose lichens where the body of the lichen is immersed within the substrate. The lichens appear as a diffuse stain of indefinite shape on the substrate and are technically known as Pyrenolichens (pie-reno-lichens).

Foliose – Folded with distinct edges which are not adhered to the substrate. Shape circular, often leaf-like.

Fruiticose – Branching lichens attached to their substrate by an anchor point. The remainder of the body is free and either erect or pendulous. (Fruiticose means branching not fruiting). Lichens reproduce their combined form asexually through the production of pustules containing clusters of photobiont cells enveloped by fungal threads or in the form of projections containing material from both parties. Dispersal is aided by wind, water, small animals (e.g. mites) and birds. Another more risky mechanism is sexual reproduction where the fungus produces its own spores, which must recombine with a suitable photobiont on germination.

Further Reading

William Purvis, 2000. Lichens. The Natural History Museum, London. Life series. ISBN 0-565-09153-0. (Distributed in Australia and New Zealand by CSIRO Publishing).

Photo Gallery

1 comment to Lichens

  • […] Lichens are a compound life form made up of a fungus and an alga. They can be seen on the leaves, branches and trunks of trees, and on rocks. They tend to predominate on the southern side of trees in the Southern Hemisphere (northern side in the Northern Hemisphere). In the absence of a compass, this growth habit can be used in navigation to provide a rough indication of North/South. […]

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