TREE LICHENS AND AIR POLLUTION SURVEY
Extension studies (optional)
a) Evaluating evidence and procedures:
When you have completed this survey, you may want to evaluate the evidence and
procedures - and consider how the approach could be used to explore questions that
you have raised about lichens.
Do you have any odd (anomalous) results?
What problems did you find which affect your results?
Can you see ways of improving the survey a) locally and b) nationally?
Much work on lichens remains to be undertaken. This survey needs to be carried out
over a wide geographical range, embracing both urban and rural sites. We hope you
have enjoyed your survey - and that you continue to explore more. You may wish to
plan your own survey.
b) Additional species
In your area you may have many unidentified species on the trunks and twigs. Using
the Key to Lichens on Twigs either in hard copy or the web-site Guide at
www.nhm.ac.uk/botany/lichen/twig you can identify more species that will allow you to see
how pollution affects lichen diversity. The species can be recorded as additional
species on the forms downloaded from this web-site on-line twig project. Recording
of additional species provides scope for post-16 students and others to find out more
about the lichen flora and how it responds to air quality and other environmental
factors in their locality.
c) Another pollution index (the sulphur index) can be calculated in a similar
manner to the nitrogen index using the sulphur-tolerant species of Hypogymnia.
Several of the questions provided in the Background Notes will help you to explore
the significance of data you collect on sulphur-tolerant species.