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
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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.
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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?
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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.
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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.
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