LICHENS 

Afrikaans:  Klipblom, Korsmors, Ligeen

German:    Fletchen

Sepedi:     Bolele  

Zulu:        Phakama

Venda:    Vhulele

 The hiking trails on Buffelskloof will introduce you to a whole new world of lichens and their incredible role in nature. Please NOTE that all the lichens, plants, and animals that you will see are here to be enjoyed. Please leave them as you find them.

 Take only photos and leave only footprints.

Do not touch.

 The word lichens is derived from the Greek word meaning “WART” or “ERRUPTION”. Lichens occur nearly everywhere, from the poles to the equator. 13500 lichen species occur worldwide of which more than 1200 species are found in South Africa.

 See lichen diagram: consists of two partners, an algae and a fungus.

 Lichens do not have stems, roots or leaves. The part that you can see growing on rocks and trees is called the THALLUS (pluaral thalli)

 Composition:

1. Upper cortex: Under magnification, a section through a typical foliose lichen thallus reveals four layers of interlaced fungal filaments. The uppermost layer is formed by densely agglutinated fungal hyphae building a protective outer layer called the cortex, which can reach several hundred μm in thickness. Beneath the upper cortex is an algal layer composed of algal cells embedded in rather densely interwoven fungal hyphae.

2. Algae layer: This part makes up 5% of the plant. It provides food for the thallus (i.e. photosynthesises) and is light loving.

3. Fungal Hyphae: The fungal part provides moisture and shelter, it is therefore the dominant partner. The thallus consists of 95% fungi.

4. Medulla: Beneath this algal layer is a third layer of loosely interwoven fungal hyphae without algal cells. This layer is called the medulla.

5. Lower cortex: Beneath the medulla, the bottom surface resembles the upper surface and is called the lower cortex, again consisting of densely packed fungal hyphae. The lower cortex often bears rootlike fungal structures known as rhizines, which serve to attach the thallus to the substrate on which it grows

 Lichens are informally classified by growth form into:

 

1. ENDOLITHIC – growing inside substrates. They are usually so well camouflaged that they cannot be seen. The rock is used to filter sunlight as strong sunlight can kill algae cells, which will lead to the death of the lichen. Endolithic lichens eventually break down the rock they live in. Look carefully at rocks that have been weathered for signs of lichen.

2.  EPILITHIC – growing on substrate surfaces. These surfaces can be as diverse as insects, rocks, leaves, bark, soil, under water and man made substrates like glass. They are visible to the naked eye.

 

EPILITHIC growth forms can be:-

CRUSTOSE – or “crusty” paint-like and flat are most commonly seen on Buffelskloof Eco-Reserve. See the brightly coloured crusty coverings on the rocks around you. They are tightly attached to the surfaces on which they grow. They grow very slowly, at a rate of about 0.4 to 3mm per year. Despite being hardy, they can be destroyed if trampled on. It can take up to 100 years for to re-grow. This is one of the reasons why we request that you keep to the designated pathways.

 

Top Left: Crustose lichen on bark. Top Right: Map lichen (Rhizocarpon geographicum) on rock.

FOLIOSE – leaf like attach themselves loosely to their substrates and can be seen on some of the trees and rocks around you. A number of folios species occur in the area. They grow faster than crustose lichens, at rates of up to 25mm per year. Various insect larvae spiders and mites use the foliose lichens for food, shelter camouflage and to lay their eggs under. Birds including the paradise flycatcher, use leafy lichens to camouflage their nests.

FRUITICOSE – bushy or shrubby, e.g. Usnea or “old man’s beard”. The strap shaped or hair-like lichens vary from minute 3cm long species to the much larger 5m Usnea species which is often seen hanging from trees around the escarpment. Fruticose lichens are the fastest growing af all lichens species with growth rates of up to 150mm per year.

     

Left: Usnea australis, a fruticose form, growing on a tree branch. Right: Reddish-coloured lichen on volcanic rock in Craters of the Moon National Monument (Idaho,USA)

Other forms also exist: leprose (powdery), squamulose (consisting of small scale-like structures, lacking a lower cortex) and gelatinous (absorbs and retains water).

ECOLOGY

Lichens must compete with plants for access to sunlight, but because of their small size and slow growth, they thrive in places where higher plants have difficulty growing. A major eco-physiological advantage of lichens is that they are poikilohydric (poikilo- variable, hydric- relating to water), meaning that though they have little control over the status of their hydration, they can tolerate irregular and extended periods of severe drought. Like some mosses, liverworts and ferns, upon desiccation, lichens enter a metabolic suspension or stasis in which the cells of the lichen are dehydrated to a degree that halts most biochemical activity. In this state, lichens can survive wider extremes of temperature, radiation and drought in the harsh environments they often inhabit.

Lichens do not have roots and do not need to tap continuous reservoirs of water like most plants, thus they can grow in locations impossible for most plants, such as bare rock, sterile soil or sand, and various artificial structures such as walls, roofs and monuments. Lichens are active when wet and inactive when dry. This means that in South Arica, certain lichens may not function for years, although they are still alive. Many lichens also grow as epiphytes (epi- on the surface, phyte- plant) on other plants, particularly on the trunks and branches of trees. When growing on other plants, lichens are not parasites; they do not consume any part of the plant nor poison it. Some ground-dwelling lichens. Stability of their substrate is a major factor of lichen habitats. Most lichens grow on stable rock surfaces or the bark of old trees, but many others grow on soil and sand.

 Lichens as food:

Lichens, to human beings, are often tasteless or extremely bitter. Their food value, however, compares well with that of cereal crops. In 1972, a Canadian pilot, started in the Arctic, survived for 23 days by eating lichens and the dextrose he had in his emergency kit.

A delicacy in Japan is a type of foliose lichen eaten in salads or deep fried fat. The Egyptians also used lichens in baking bread to give it an unusual flavour. They relished this bread to the extent that they imported shiploads of lichens for it.

 Animals that eat lichens include various bagworms, butterflies, moths, snails and slugs. Springbok in Namibia and Gazelle in the rest of Africa have been noted feed on lichens. Reindeer and Caribou feed almost exclusively on lichens during the winter months. Sheep in Libya today are still grazed on a foliose lichen, Lecanora esculenta. This lichen occurs in the deserts of the Middle East and is suspected to be the manna used by the Israelites during their exodus from Egypt.

 Other uses of lichens

Lichens are vital in nature for:

    -      Oxygen and carbon dioxide cycles

    -      Soil formation

    -      Food for certain animals.

They are also used in:

-          Perfumes

    -      Traditional beers

    -      Traditional medicines

    -      Antibiotics

    -      Preservation of mummies.

 

Toilet soap and perfumes are manufactured by the French.

Lichens are used medicinally:

-   Scandinavians use it as a substitute for penicillin.

-   Finland use it to fight fungal and bacterial species.

-   Germans use it to treat certain skin diseases.

-   Xhosa use foliose lichen to remedy toothache.

 

Various lichen acids are used to fight certain plant mildew.

Also used in Litmus paper used in chemistry – to determine if something is acid or alkaline.

Lichen acids have been used as a natural wool dye for centuries in Scotland and Ireland.

 

lichens indicate pollution:

This was shown in Pretoria, where no lichens grow on Jacaranda tree trunks in the industrial area. However in the eastern suburbs of the same city a mosaic of up to 18 different lichens grow on a tree trunk. Lichens absorb all dissolved substances that come into contact with them e.g. heavy metals and radio active levels increase in the animals which browse on those lichens. The meat of these animals may be dangerous for human consumption. After Chernobyl, reindeer meal was unfit for people to eat. 

Preservation of mummies: The internal organs of the mummy were removed and the empty cavity then packed with lichens, sawdust, brewer’s myrrh and all sorts of spice. It is not known whether the Egyptians used the lichen for its preservative or aromatic qualities or simply as a light weight packing material which was highly absorbent. 

 lichens form soil

BIOLOGICAL WEATHERING

Endolithic lichens loosen the grains of the rock they grow in. The rocks break down to form new soil. As the rocks disintegrate, minerals that have been looked into the rocks for hundreds of millions of years are released. This is called the biological weathering of rocks. It was found that endolithic lichen (Lecidea sarcogynoides) weathers sandstone at a rate of 1cm per 100 years.

 BAGWORMS

There is a species of bagworms that uses loosened quartz grains in rocks to build it’s bag. This bagworm species contributes 5 tons of new sand to the ecosystem of the Golden Gate Highlands National Park each year. Another type of bagworm is found near Graskop. It eats crustose lichens and also uses quartz grains loosened by endolithic lichens to build it’s bag.

 LANDSCAPES

Through this weathering process, endolithic lichens give rise to the amazing landscapes and shapes one often sees on weathered rocks. Feel the surfaces of the various rocks with all their little potholes and ridges.

 MICRO ECOSYSTEMS FORMED

Water, used by animals such as lizards, frogs and insects accumulates in these little rock pools. Algae, fungi, bacteria and various small animals also live in water, creating small ecosystems. These pools eventually fill up with organic material and sand so that plants can grow in them.

 lichens favorite music is…… rock

Approximately two thousand million years ago this area was covered by a huge inland fresh water sea. Mud, sand and other layers were deposited. The pressure of these layers on each other and the drying effect of the sun changed the muds and sands into the rocks that you see here today. Sand delta was transformed into sandstone and quartzite. Muds were changed into mudstone and shales, and where they contained bicarbonates, dolomites was deposited.

 These three types of rock are quite different.

DOLOMITE

Dolomite is a greyish colour and very “wrinkled”. The Afrikaans name for dolomite is elephant or old rock. Dolomites are made up mainly of calcium magnesium carbonate, and so are soluble to a limited degree. Weak carbonic acid (rain water) dissolves away dolomites to form caves and sinkholes. The many caves found in this area, including the Echo and Sudwana caves, bear testimony to this. Dolomite contains the oldest known fossils – stromatolites – which appear as home shapes in the rock and were formed by algae growing on the floor of the sea.

 QUARTZITE

Quartzite is the most common rock that you see around you. It varies from grey to dark black and most of the rock along the pathways is Black Reef Quartzite. Most of them are rough, but where water has flowed over them, they are fairly smooth. Many quartzites stand in small pillars with little “fairy landscapes” on top of them. The cliffs in this area are quartzite.

 SHALE

Shale is a soft rock and is often used in this area to make ashtrays and carvings. The pathways are mostly made of shale. You will see that many of the shales have ripples on them which indicate water flow. Most of the smooth rolling hills in this area are formed by shales and dolomites.

 INFORMATION ON LICHENS WAS RESEARCHED FROM THE INTERNET AND FROM LITERATURE AT THE BURKES LUCK LICHEN TRAIL, SUPPLIED BY PROFESSOR DIRK WESSELS OF THE UNIVERSITY OF THE NORTH.