Investigation into how Lichen growth is affected as you move further away from a river

After having done a preliminary trial run, I chose not to include soil/tree root and grass in my official results as they would have no bearing to my investigation as a whole. I made no other alterations to my method.

Method

For the main experiment I selected 3 sites where there was a river and selected a spot at each randomly. To ensure I selected the spot randomly I download an app which randomly generates coordinates in the area you are located. The coordinates which the app generated I used those as my starting point. I used the app to generate new coordinates at each site. This is a more reliable data collection method as a person might be more inclined to start from a point which seems more appealing or has a higher chance of collecting data which could lead to data bias.  

Then I did a 10m line transect from the river to the embankment and recorded any lichen every 2 m. I then moved the line transect 2m down the river and repeated the experiment. I did this until I had moved the line transect 10m from the original location that I stated at.

Apparatus:

• Quadrat (1 meter x 1 meter)
• 15 meter tape

Justification for Apparatus used:

A quadrat is a square used in ecology to isolate a sample, usually about 1m2. The quadrat is suitable for sampling plants, slow-moving animals (such as millipedes and insects), and some aquatic organisms. When an ecologist wants to know how many organisms there are in a particular habitat, it would not be feasible to count them all. Instead, he or she would be forced to count a smaller representative part of the population, called a sample. A suitable size of a quadrat depends on the size of the organisms being sampled. For example, to count lichens, one could use a quadrat with sides 0.5 or 1 meter in length.

I used a measuring tape as it the only tool that is readily available to measure a 10m length. It has been manufactured so that there would be small systematic error. As the distance increases the % error would decrease as the systematic error would always be the same.

Risk Assessment:

Observing & Recording:        

Results:

Site 1: River Pont

Site 2: River in Richardsondees Park, Wallsend

Site 3: River Wansbeck, Morpeth

As for anomalous results, it is very hard to identify results which are anomalous as lichen growth is not something that can be quantified as anomalous or not. For the purpose of this investigation it has been assumed that there are no anomalous results as it cannot be said if lichen growth should or should not be present and what % cover there should for a particular lichen growth.

Interpreting & Evaluation:

Looking at the results it can be said that as you get further away from the river bank the abundance of Lichen reduces. By using spearman’s rank correlation it is possible to show a positive correlation between the distance from the river bank and lichen abundance. The equation for the spearman’s rank correlation is:

Where d is the difference in the rank number and n is the number of pairs of data. If the value is close to -1 then there is a negative correlation. If it is close to 0, then there is no correlation and if it is close to +1 there is a positive correlation. To calculate the spearman’s rank correlation, I ranked the total lichen abundance at each site in descending order and I ranked the total distance from the river line in descending order. Then I found the difference between the two. I then squared each of the values to remove the negative sign in any answers then added up all the d2 and times this value by 6 to give me the top value in the equation stated above. I then totalled the number of different pairs of data. I then multiplied this value by the total pairs of data squared minus 1, which gave me the value for the bottom part of the data. I then divided the vale for the top part by the value for the bottom part of the data. This gave me the spearman’s rank correlation for each site. The values are listed in the table below:

For each site there are 36 pairs of data so the critical value will be 0.330. For values which are equal or above the critical value you reject the null hypothesis and value below the critical value you accept the null hypothesis. As for each site the Spearman’s Rank Correlation is above the critical value the null hypothesis that there will be no difference in growth and abundance of lichen as you move away from the river bank is rejected. This means that the experimental hypothesis as you move further away from the river bank lichen growth will increase and there will be less abundance of species is accepted.

This is because many lichens break up into fragments when they are immersed in water, dispersing them by wind action, to resume growth when moisture levels drop to an acceptable level. There has been an experiment over the course of 15 months which shows that lichens immersed in water for prolonged periods of time will not grow as successfully as lichens which have standard water contact.

I have included below the data for each site, which has been ranked, and the difference calculated and squared to remove any minus sign. The table below will show how I calculated the Spearman’s Rank Correlation.

I have plotted a graph showing the average correlation between distance from the river bank and lichen abundance. This shows that there is a general positive correlation on Lichen growth and distance from a river bank. The graphs do not show a complete linear relationship but this is to be expected as there are a lot of environmental factors. These graphs are shown below:

It can be concluded that from the spearman’s rank correlation values that there is a positive correlation between water abundance and lichen growth. The further a person moves away from a river bank the greater the abundance of lichen. This is due to the fact that Lichens absorb water and minerals from rainwater and directly from the atmosphere, over their entire surface area. They are not able to absorb water and minerals as efficiently if they are immersed in a fast flowing river as there would be no time for the lichen to absorb any minerals as effectively as diffusion is not quick enough to occur. This leads to many lichens break up into fragments when they are immersed in water, dispersing them by wind action and some are carried away by the river, to resume growth when moisture levels drop to an acceptable level. There has been an experiment over the course of 15 months which shows that lichens immersed in water for prolonged periods of time will not grow as successfully as lichens which have standard water contact (standard water contact was stated in the experiment to be 4-7 hours a day)6. During prolonged dry periods, lichens survive by retaining a small amount of water and reducing their growth and metabolic processes to the barest survival levels. After a rain, the fungal partner is able to soak up water like a sponge, absorbing two to three times its weight in water. A moist internal environment is critical for the alga, which needs water, along with carbon dioxide and sunlight, to manufacture food through photosynthesis7. During dry periods when other food may be lacking, the fungus benefits by absorbing sugars and nitrogen-rich compounds produced by the alga during photosynthesis. In some cases the fungal partner is parasitic, using special fungal hyphae called haustoria to penetrate the algal cell and absorb nourishment. Since the fungal partner usually does not kill the alga, some scientists call this relationship a controlled parasitism of the alga by the fungus7.  But if the Lichen is completely immersed in water, then it does not absorb water fully. Also Lichens manufacture food via photosynthesis, which it cannot do if it is not getting sunlight and a plentiful supply of carbon dioxide. But looking at the graphs on the previous page there seems to be a weak, if any, positive correlation between Lichen abundance and distance from a river bank in the graphs for site 1 and 2. However there seems to be a distinct positive correlation at site 3. By looking at the graphs for site 1 and 2 it is hard to see if there are any anomalous results as the trend is not so clear and obvious. By looking at the graph for site 1 and the spearman’s rank correlation it can be said that there is some sort of positive correlation but not as a high positive correlation as in site 3. So the experimental hypothesis as you move further away from the river bank lichen growth will increase can be justified as the data collected and the spearman’s rank correlation shows that lichen growth increases as you get further away from a river bank. But there are other limiting factors which affected the data collected which I have discussed in the next section.

Evaluation:

There is scope for improvement in my investigation. I have outlined below how the investigation could be improved.

Error:

There are three types of errors; mistakes, systematic errors and random errors.

• Typical mistakes include reading the wrong numbers from a tape measure, making a measurement with the tape snagged or reading the wrong values from the tape when processing the measurements.
• Systematic errors are ones that can be repeated and can be accounted for in processing. If you calibrate a tape measure against a known standard and find that it always measures distances that are too long, the difference is a systematic error and can be removed when the measurements are processed.
• Tape measurement made several times under the same conditions is unlikely to give exactly the same value for each measurement. Judgement of the tape reading will vary as will tension on the tape depending on how hard you pull. If you remove the mistakes and the systematic errors then some variation in the repeated measurements will still be seen, this is called random error.

To fix the systematic error in the tape, I took two other tapes and measured 1 meter with all three tapes. Two of the tapes were 5 meters long so I could not use them as they would not be long enough for my investigation, so I had to use the 15 meter tape. According to the two different 5 meter tapes, the 15 meter tape was 0.cm out i.e. it was 0.5 cm to long. To rectify this problem when I placed the quadrat on the ground, I would place it 0.5 cm further back.

The readings I collected were collected at different days for each site therefore there would have been some factors which might have affected my results. For example it had rained in Morpeth so river levels might have been higher and the flow rate increased which could have dislodged some lichen from rocks. This also means that the edge of the river bank location changed so I would have not measured the line transect accurately. But the distance from the edge of the river would have had little impact on my results as the widths of rivers are constantly changing. The error in identifying the lichens present was kept to a minimum because I used the Lichens: an Illustrated Guide to the British and Irish Species by Frank Dobson which is a comprehensive guide to lichen species in the British Iles. This guide would have been subjective to analysis and reviews before publishing. The edition I used was the third edition, as there had been some errors which had been rectified by the publishers.

When I was calculating the % cover of Lichens by using a Quadrat I would round % cover up if the lichen was covering more than 50% of a square on the Quadrat. This would alter my final results slightly but not significantly.

Limitations in the investigation were that I was not able to collect data at all three sites at the same time as that was not physically possible and this would have lead to environmental change at each site. Another limitation was the sites I had chosen were in different locations in towns which were in different stages of development. This would have inadvertently leaded to lichen growth as lichen is good indicators of pollution. I tried to counteract this by choosing my sites with similar exposure to pollution but it hard to be completely accurate. Another limitation in the investigation was that when the % cover of Lichens against Line transects distance on a graph, there seemed to be no distinct correlation. This is because there is no completely distinct and clear cut answer to my investigation. There are many factors which contribute to lichen growth so overall it would be hard to judge if there is a causation and correlation based on one factor.

I could have further modified my investigation by using my data to see if certain Lichens are more predisposed to grow in locations where water and moisture is more abundant. To do this I would have had to take the following abiotic factors (in table below) into account as certain Lichens grow better in certain condition.

Bibliography:

1. Gilbert, O. 2004. The Lichen Hunters. The Book Guild Ltd. England.
2. Hawksworth, D.L. and Seaward, M.R.D. 1977. Lichenology in the British Isles 1568 - 1975. The Richmond Publishing Co. Ltd., 1977.
3. Lichens: an Illustrated Guide to the British and Irish Species by Frank Dobson
6. The Response of Lichen Growth to Additions of Distilled Water, Rainwater and Water from a Rock Surface ,R. A. Armstrong, New Phytologist
   Vol. 79, No. 2 (Sep., 1977), pp. 373-376
   Published by: 

The sources stated above are sources I have used for my investigation though I did not use them exclusively in my research and rational section. I am going to evaluate my sources for credibility.

Source 1: This source has been published by an independent publishing company called The Book Guild Limited. On their website it has been stated that the book has been peer reviewed and amended by British Lichen Society and . Both organisations have a reputation for be accurate and up to date with recent developments. This book is also recommended by the Field Studies Council so it must have been deemed to have accurate information.

Source 2: This book was mainly used for background information on Lichens. At the time of print this book had been reviewed by Cambridge University so it is expected to be reliable. But when I was cross checking this book with other sources I found that the book was outdated in some aspects, so I have chosen to remove any information that was outdated from my investigation.

Source 3: I used this book in the fieldwork section of my investigation, when I was identifying the different types of Lichens. This book was published in conjunction with . This means that  contributed towards this book and reviewed it before it was published. This book is also recommended by the Field Studies Council which suggests that this book is reliable and accurate.

Source 4 & 5: These sources were from the Field Studies Council official website so they would have been checked and reviewed before published. I checked the data in these two sources against other identification charts from  and the  which both had the same information. So this source is reliable.

Source 6: This paper from the New Phytologist journal was published in September 1977. It has since then been peer reviewed 19 times and has been accepted by the wider scientific community according to New Phytologist (this was stated on their website on 13th October 2012). So this source is deemed reliable.

Source 7: The material in the website is based upon work supported by the National Science Foundation under Grant No. 0137759. This source is an official site of a research university called University of Colorado Boulder. The information from this source has been published and peer reviewed in the National Science Foundation journal so is considered reliable.

Sources for Research and Rational:

1. Ahmadjian V. (1993). The Lichen Symbiosis. New York: John Wiley & Sons.  .
2. Brodo, I.M., S.D. Sharnoff, and S. Sharnoff, 2001. Lichens of North America. Yale University Press, New Haven.
3. Gilbert, O. 2004. The Lichen Hunters. The Book Guild Ltd. England.
4. Haugan, Reidar; Timdal, Einar (1992). "Squamarina scopulorum (Lecanoraceae), a new lichen species from Norway".  12 (3): 357–360. : .
5. Hawksworth, D.L. and Seaward, M.R.D. 1977. Lichenology in the British Isles 1568 - 1975. The Richmond Publishing Co. Ltd., 1977.
6. Kershaw, K.A. Physiological Ecology of Lichens, 1985. Cambridge University Press Cambridge.
7. Kirk PM, Cannon PF, Minter DW, Stalpers JA. (2008). Dictionary of the Fungi. (10th Ed.). Wallingford: CABI.  .
8. Knowles M.C. (1929). "Lichens of Ireland". Proceedings of the Royal Irish Academy 38: 1–32.
9. Purvis, O.W., Coppins, B.J., Hawksworth, D.L., James, P.W. and Moore, D.M. (Editors) 1992. The Lichen Flora of Great Britain and Ireland. Natural History Museum, London.
10. Sanders W.B. (2001). "Lichens: interface between mycology and plant morphology". BioScience 51 (12): 1025–1035. : .
11. Seaward M.R.D. (1984). "Census Catalogue of Irish Lichens". Glasra 8: 1–32.
12. Whelan, P. 2011. Lichens of Ireland. The Collins Press, Cork, Ireland.

I have reviewed all of the sources stated above which I had used in the research and rational. I have summarised my findings in a table which is shown below:

Vikram Mahal    13SFI      A2 Biology Coursework