LICHENS

  

 General
 information
 Lichens growing
 on the trees
 and overground
 lichens
 Lichens
 on the rocks
 and multi-
 habitat
 lichens
 Monitoring
 The role
 of lichens
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Text:
Anna
Krzysztofiak

Photos:
Lech Krzysztofiak

Drawings:
Anna Krzysztofiak

Webdesign: 
KAJA
 
2003

  

  

  

The role of lichens

  

There appear plants behind the lichens
growing on the rocky substrate

  

The role of lichens in the functioning of the ecosystems is often underestimated; after all they play an important role in nature as pioneer organisms. They grow on the rocks and in the extremely poor environments where only bacteria and algae used to live. Lichens produce specific chemical substances (organic compounds, derivatives of fatty acids and phenols) which have germicidal, bacteriostatic or poisonous properties. As the result, these substances accelerate the rate of weathering processes on the rocks where they grow. Thanks to that there appears a thin layer of soil which breeds the spores of bryphyles and pteridophytes and the seeds of higher plants.

  

Porpidia crustulata grows on the naked rocks

The pioneers of life, the first inhabitants of rocks are small shell-like lichens. After some time they are replaced with the leafy and bushy lichens. It can take from 5 to 20 years for lichens to settle the rocks. Meanwhile the unequal surfaces of cortex stop and gather dust, powder, mineral waste and organic matter. Apart from the shell-like lichen, there appear the bushy lichen - Cladonia on the sandy dunes which have an essential influence on the formation of humus layer.

  

Lichens are an important element of life of many species of invertebrates as they give them a shelter and provide a source of food for them. It is estimated that about 300-400 species of invertebrate animals is dependent on the lichens to a large or small extent. Also, some species of vertebral animals such as caribou, musky oxen and reindeers eat mostly lichens. The reindeers' menu includes about 50 species of lichens, mainly growing on the ground such as: Cladina stellaris, Cetraria islandica and Cetraria ericetorum. Some species of birds use lichens to build their nests and thanks to lichen's antiseptic properties they are protected against the bird's parasites.

  

The trees are often covered
with a thick layer of lichens

Also, the lichen regulate and shape the microclimate and the moisture in the environment thanks to the ability of absorption of large quantities of water from fog, dew and other atmospherical rainfall. By this ability they are a factor which contributes to maintaining long-term and steady moisture in the forest. The lichen growing on the trees in the forest area of 1 hectare are able to retain up to several hundred of liters of water.

  

By producing "the lichen acids" some lichens have a positive influence on the development of microflora of soil which helps in the creation of humus and germination of seeds. Chemical compounds produced by the epiphytic lichens protect the trees against fungal infections.

  

Man has been using lichens for ages, too. Lichens are used during the dying of cloths; in the perfume-cosmetic industry lichens are used to fix the scents. Also, lichens are used for the production of litmus and the substances fighting the herbivorous insects and snails. Lichens are also indicators at dating the rocky substrates. Knowing the increase rate of the thalli one can estimate the age of the thallus and indirectly point to the construction time of some objects, e.g. buildings, statues or rocky slides. Extremely poisonous vulpine acid, produced e.g. by Vulpicida pinastri, was used for preparing the poison for wolves and foxes.

  

Vulpicida pinastri contains
a strongly poisonous vulpine acid

The curative proprieties of Usnea hirta, Cetraria islandica, Cladonia coccifera or Xanthoria parietina have been known in natural medicine for ages. In 1749 Linnaeus presented some detailed descriptions of lichen's usage in medical care. For example, he recommended the usage of Parmelia saxatilis to make tampons which would obstruct hemorrhages. Also, he suggested using Cladonia coccifera as an antitussive medicine. Practically lichen were commonly used to cure cold, cough, tuberculosis, epilepsy or even to help the hair grow.

  

The present medicine still uses the curative proprieties of some lichens, e.g. Cetraria islandica is used to produce a practical cure for the bronchitis of respiratory track, gastric and duodenum ulcers and Cladonia lichen are used as the antibiotic specimens.

  

Xanthoria parietina was used
as a cure for jaundice

Despite their low nourishing values the lichen became the components of many national cuisines e.g. the Japanese consume Umbilicaria esculenta and Alectoria pellucida and the ground thallus of Cetraria islandica is added in Lapland to bake bread. Probably the biblical "manna" was Lecanora esculenta - the lichen whose packed thallus could be carried far away by wind. At present this lichen is consumed by the Bedouins' tribes which lead a nomadic lifestyle on deserts.

  

As the lichens are sensitive to any atmospherical air pollution, especially caused by sulphur dioxide, they are often used as indicators of cleanness of air. To estimate the degree of air pollution people use the so-called lichen scales based on the differences of sensitivity to the concentration of SO2.

   

   

   

 

  

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