What am I ?????

My name is “Golden Shields”, or “Xanthoria parietinar” in Latin

• I am a lichen• I am found growing on rocks, walls and trees• I am one of the most common lichens found

today in our towns and cities• I am even found in London

What are lichens?

• Unlike trees, grasses and flowers, lichens are not a single plant

• They are actually composed of two organisms living together in a symbiotic relationship…

• A blue-green algae which photosynthesises to make food, and a fungus which creates a “body” in which both partners live

Types

Leafy (foliose)

There are about 30,000 species of lichen worldwide, covering 8% of the land surface. There are 3 main types…

Shrubby (fruticose)

Crusty (crustose)

Why study lichens?

• They grow just about everywhere

• They tell us about the health of our environment

• They are very useful; - as recyclers of nutrients, providing homes for insects, humans extract dyes from them, eat them, use them as ingredients in drugs and cosmetics

Lichens and air quality• Lichens are very sensitive to sulphur dioxide

(SO2) pollution in the air – from industry and burning fossil fuels, especially coal

• They absorb it dissolved in water

• It destroys the chlorophyll in the algae preventing it from photosynthesising and killing the lichen.

• Levels have fallen since the 1970’s

Nitrogen pollutants

• Nitrogen compounds from traffic on roads and from intensive farming (fertilisers) have become major pollutants

• Town and country areas can be affected

Bio-indicators

• Lichens are widely used as environmental or bio-indicators

• If the air is clean, shrubby, hairy and leafy lichens become abundant

• If the air is polluted more tolerant crusty lichens are present

• In extreme cases of high pollution, there may be no lichens at all (lichen deserts)

Fieldwork aims

• To survey and identify species of lichen on the trunk and twigs of selected trees

• Assess levels of pollution by examining the pollution tolerance of lichen species found

• Compare and contrast different areas

How?• You are going to survey

both trunks and twigs of tree species with acid bark

• Choose from; Oak, Birch, Cherry, Alder, Sweet Chestnut, Rowan, Hornbeam.

• Use the “Which tree?” resource to help you identify these species

Trunk

• Tree trunks are the oldest part of the tree• Some lichens grow very slowly and tree

trunks may carry a long-established colony of lichens, as long as environmental conditions have not been altered

• You will choose three trees (with accessible trunks) of the same species at each site to survey

Twigs• Every spring new twigs are produced –

this is the youngest part of a tree.• In good conditions lichens rapidly colonise

new twigs• You will sample non-shaded twigs of about

3-4cm thick at the base, in on one or more trees of the same species

• You will sample 10 twigs in total at each site

Identification

You will need to identify…

1. The tree species (using the ‘which tree’ resource)

2. The lichen species (using the key / chart provided by your teacher)

Recording

• Your teacher will go through the recording sheets with you

• You must fill in the recording sheets…

1. Fully2. Clearly3. Accurately

Follow-up

• You must use the data you collected at each site and recorded in the field work booklet

• Complete the ‘follow-up resource’ to summarise your main findings and make judgements about the environmental conditions at each site

Extension

• Your field work can be written up formally, as a proper investigation

• You must use the ‘investigation write-up resource’ to help you to plan, structure and write it