MORE ADVANCED PROJECTS
A Walls (Key Stage 4)
Guidance on method:
a) What kind of stone is in the wall?
b) Is there cement or mortar?
c) If you have no pictures or books or help in identifying a few of the lichens, just give them your own names or a letter of the alphabet.
d) Can you take the same kind of wall and look at the north face, south face (also east face and west face possibly) and the very top of the wall?
e) Can you measure the light on the north, south and top? Do you have a photographic light meter?
f) Take a metal coathanger and bend it into a square shape. This can be used for sampling. It is called a quadrat. Place this on the south side near the upper middle of your wall and estimate the percentage cover of each kind of lichen you see in it, Record these figures in a chart.
g) Repeat this for the north side of the wall nearby. Repeat at the top as well. At the top it may be too narrow for your quadrat so you can add together two or three samples.
h) You should repeat sampling (5 times) on the wall on the south and north and on the top and add together your percentages of each kind of lichen for the south, north and the top of the wall. If you divide by 5 for each lichen species for the south, the north and the top of the wall, you will get the average percentage cover for each of the lichens.
i) Use a camera to take photographs of representative samples of your wall (north, south and top).
To help with your discussion and conclusions
a) Do you find the same kinds of lichens on the south, north and top?
b) Do you find more lichens (less bare surface and more lichen coverage) overall on the south, north or top?
c) Do you find more kinds of lichens on the south, north or top of the wall?
d) You can run a chi-square a statistical test of your results, having started with a null hypothesis stating that there is no difference
Once you have done the field work you can answer these questions and come up with some conclusions about how lichen growth is affected by light.
It is true that you could also investigate moisture or whether the same lichens grow on mortar or on the rock - but these are different studies because you would be looking at the effect of different factors on lichen growth.
B Air quality (Post-16)
Guidance on method
a) You must define the area (which should have a variety/range of habitats related to possible pollution levels - or you should define contrasted areas (but beware of geographical differences). You will need a map of the area so that you can mark where you have sampled and note with reference to the map where and what lichens have been found.
b) You can apply the null hypothesis which states that there is no difference in lichen abundance (frequency, diversity) throughout the area or between the chosen areas.
c) Sulphur dioxide was once the big problem, making substrates more acid. Now its effects are quite diminished and lichens which had been intolerant are now returning into areas once poor in lichens.
d) Today we are faced with another problem: airborne nitrogen compounds and phosphates from agricultural fertilisers and traffic exhaust making substrates more alkaline and actually reversing the effect seen from the acid effects of sulphur dioxide and acid rain! So you must be cautious about what you are investigating.
e) You are likely to look at lichens on trees. You should chose the same tree throughout your study (bark pH of different tree species is different - eg conifers are acid, oaks rather more acid than sycamores and ash which are more neutral; elms - alas mostly gone - are basic) and decide whether to look at trunks or twigs or both. Think through sampling and recording procedures carefully before you begin.
f) You can record all the lichen species for a chosen tree sample - or you can select certain 'indicator' species and record their abundance and distribution. Before you decide on your precise method, you should make some general observations of the lichens distributed on the tree or trees you choose - no point in selecting an indicator species which never is found!
g) Use a camera to record representative results.
h) You should aim to test your hypothesis statistically (chi-square test) when you have completed your records.
Guidance with discussion and conclusion
a) Your statistical test will enable you to make a conclusion for your study.
b) If you find differences, you should discuss suggestions for the difference in your discussion section of your report.
c) Can you relate any difference to a difference in factors which you have explored or are apparent when looking at the tree positions on your map?
C Church Walls (Post-16)
Preliminaries
1) I suggest that you start out with the null hypothesis: 'There is no difference in the abundance and distribution of lichens on the north- and south-facing walls of a church (or name the particular church).' You then will be able to test your results with the chi-square statistical test which in turn will enable you to make statistically valid conclusions. (You may have access to an appropriate software program.)
2) You must take care in selecting the areas of wall to be certain that they are similar in every detail, except aspect. For example, the construction and age of the walls should be the same: similar kind of stone and pointing in mortar or cement. Be certain that there is no obvious shade from trees, buildings or nearby walls - or marked effects from traffic or agriculture.
3) Decide on a few lichen species for recording, eg Dirina stenhammarii, Diploicia canescens,Caloplaca citrina and C. flavescens. You should indicate whether each record is on stone or on mortar/cement.
4) You must sample in exactly the same way on both walls. Different methods (described below) are available and you may need to have an initial trial before you decide on the best for your study. In all cases you need to define the total area of each wall (the same for each) which you are sampling. You must decide on the height above the ground for your area (eg 1.5m) and stick to this height on both walls. Measure and chalk marks to indicate the area.
METHOD A
Working along the chosen height, use a tape measure or meter rule to provide points at intervals of 5 or 10cm along a line transect. At each point at the designated interval, record for your named lichens, 'other lichens', bare stone or bare mortar. You need at least 100 points for each wall to get a good result, bearing in mind that at some points you will not touch one of your chosen lichens.
METHOD B
Use a quadrat (if your school does not have one or one of appropriate size make one out of a metal coathanger or bamboo/garden stakes). A suitable size is 0.25m square, although if the wall is well covered a smaller size used more frequently (closer intervals) may give better results. Place this in the same way along the chosen height line - this time at meter intervals - so as to have at least 10 quadrat placements on each wall. Place the quadrat in the same way each time (eg top on the height line, left upper corner on the measured interval mark). For each quadrat you will need to estimate and record the percentage cover for each of your chosen lichens, 'other lichens' (and mosses?) and bare stone or bare mortar. All of this information will be useful in testing your hypothesis and drawing up your conclusions.
METHOD C
Use you height line as a starting point and use one meter intervals along it. You will need to carefully chalk these points in from 0 to 9 Arrange vertical points downward from your height line so as to give you points 0 (top) to 9 (bottom). The intervals will, of course be less than one meter (20 cm or less). You now need to place your quadrat at random in this area by choosing numbers at random using a table of two-digit numbers (or carefully generating two-digit numbers at random from a calculator). Each two-digit number defines the co-ordinates (points) for sampling. Always locate the co-ordinates generated by starting from the upper left corner of your area. Put the co-ordinate point in the centre of your quadrat and record percentage cover as in Method B. You should record for a minimum of 10 quadrats on each wall - 20 would be better. This method has the advantage of disregarding height and because it is random (not regular) gives a better idea of the distribution and abundance of the lichens on the whole wall. Beware, however, of drainpipes, windows and doors which may interfere.
5) Whichever method you choose, record in a carefully designed table or spreadsheet. You will need to add up results for your lichens and then divide by the total number of points or quadrats to provide you with an overall figure for each wall.
6) Use a simple camera to illustrate your method and select representative portions of the walls to illustrate your findings. Colour prints will be useful as part of your recording.
7) You must work out methods to measure differences in light intensity and moisture so as to relate or correlate your distribution results to one or both of these physical factors.
a) Light: Do you have access to a photographic or selenium light meter (see physics dept)? You must take readings at different times of the day on both walls and repeat on another day. In using these meters, don't worry about the units - relative figures will suffice. You may have an electronic environmental meter with light reading facility (and possibly also humidity or moisture reading potential).
b) Humidity: You may need to use a hygrometer (see geography dept), or cobalt chloride paper - time for dry (blue) to wet (pink) to indicate relative moisture on the two walls. Be certain that if you measure on the wall directly you use the same height position for each wall.
It would be very valuable if you could repeat your study on another church, having once completed the first. It would be interesting to see if you obtain the same pattern of results. This would therefore provide results suited to correlation testing.
For further study: If you adopt Method A or B for your study, you could repeat the sampling at another height - but this introduces another variable and this becomes another study whereby you are comparing distribution and abundance at different heights on the same wall - not between the two wall aspects. This further study could provide results suited to correlation tests.
1