Is the preferred habitat of moss on the North side of a Yew Tree or the North side of an Oak Tree?

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Richard Tandy

Richard Tandy

A2 Biology – Ecology coursework

Is the preferred habitat of moss on the North side of a Yew Tree or the North side of an Oak Tree?

Plan of investigation

For this project I aim to investigate if moss coverage has a preferred habitat on the North side of a Yew tree (a coniferous variety) or the North side of an Oak Tree (a deciduous variety). I will undertake this by means of fieldwork in a woodland area and the sampling and collection of data in the natural habitat of the forest in which I will visit.

Appropriate Equipment to be used

For the investigation I will need:

  • A compass
  • A quadrat (approximately 10cm × 10cm)
  • A meter ruler
  • A notepad to record results on to
  • A paper bag to protect notepad from the rain
  • A pen
  • String measured at approximately 1.5 meters long
  • Appropriate clothing such as waterproofs and walking boots

On a separate A4 page is a drawing of the table I will use to record my results, showing the readings I am planning to take.

The procedures selected and anticipated methods of collecting data.

I will need to control various techniques and methods of working in order to standardise my investigation.

I will standardise the actual sample taking. I will place the meter ruler against the trunk and place the quadrat at a height of one meter, with the bottom left hand corner of the quadrat touching the top right hand corner of the ruler. I will count the amount of squares placed over moss to derive a percentage. I will do this twice.

Using the compass I will ensure the moss I am sampling is on the north face of the tree, as I specified in my aim. Using the string I measured, I will standardise the circumference of the trees, selecting trees only with a circumference of around 1.5 meters long. I will also try to make sure all the trees are roughly of similar height. These two variations relate to the age of the tree and this is a factor which could influence the amounts of moss growth. I will be certain to use the same quadrat size for the whole investigation (10cm × 10cm). In using this quadrat size I will be surveying a reasonable area of the trunk and it is not too small, something which would probably give an unfair representation of the moss coverage in that area.

  I will furthermore try to make certain that the surroundings of each tree are similar, for example some areas may be more open to the elements such as the prevailing wind and this could influence moss coverage. I will try to some extent to ensure there is similar light availability at each area I sample by surveying the amounts of canopy cover for example.

I will take percentage moss coverage recordings from 15 Yew Trees and 15 Oak Trees. I believe a larger data set such as this will lessen the effect of any potential anomalies in my results and give more reliable overall results.

There are numerous factors I will not be measuring but they may have an effect on my results. Light availability (in relation to canopy cover), rainfall, moisture levels, bark texture and characteristics, the season (time of year), the type of forest, soil depth and pH are some examples. I cannot control these but I will be able to analyse their influence on my results.

I will sample in choosing trees in and around the same area so that factors such as light availability, soil types and moisture levels are kept as constant as possible. I will also sample trees with similar characteristics. I will standardise the circumference of the trees by sampling trees with a similar circumference (1.5 meters). This will also ensure the trees I sample are all of similar age and height. This is necessary because these are factors which could influence the amounts of moss growth. For example, a more established tree could have more branches and canopy cover which equates to less light availability for instance.

How the data will be analysed

As well as recording the data clearly in a table, I will draw two graphs: a bar graph and a scatter graph. Both will have the same axes, as shown (diagram 1), and will illustrate the relationship between the type of tree (Yew or Oak) and the percentage moss coverage from each of the 30 sites. I will also draw a bar chart to compare the average percentage moss coverage from both tree species, cumulating all of the readings (diagram 2).

Statistical test

The statistic I will use to asses whether or not my results agree with the null hypothesis will be the Mann-Whitney U test. I will use this statistic because I am planning to collect a series of replicated measurements of one variable. I will need to make sure I collect at least six replicates, and I will compare this set of data against a second set.

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  • Null hypothesis H0 definition:

The statistical hypothesis that states that there are no differences between observed and expected data.

The Null hypothesis H0 for my investigation will be:

There is no difference in the amounts of moss coverage on the north side of a Yew tree and the north side of an Oak tree.

The alternative hypothesis Ha for my investigation will be:

There will be a difference in the amounts of moss coverage on the north side of a Yew tree and the north side of an Oak tree.

Why the North ...

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