Epping Forest Biology Field Study

Background Information:
Oak trees are occasionally covered on one side, with an orange looking substance. This is due to the presence of a simple alga called Trentepholia aurea (Trentepholiaceae). It is made up of filaments of cells that contain high concentrations of carotene, giving it the bright orange colour.

Hypothesis: The Trentepholia aurea will be found on the north side of trees, as this is where they
receive the least amount of direct sunlight.

Null Hypothesis: Trentepholia aurea is not affected by aspects of a tree.

Variables:

Dependent Variable – I am measuring the percentage cover of Trentepholia aurea on four different
aspects of a tree (North, south, east & west)

Independent Variable – The dependant variable will be plot against the aspect of the tree.

Control Variable

Affect on results

Means of monitoring control

Oak tree

Different types of trees may encourage a faster Trentepholia aurea growth rate than others.

Ensure only algae on Oak trees are recorded.

Temperature

Warmer temperatures promote growth of living things more than cooler temperatures, therefore increases rate of Trentepholia aurea growth.

Thermometer

Light intensity

Living plants need sunlight in order to grow. Therefore light will further the growth of Trentepholia aurea.

Light meter

Equipment:

Equipment

Use

Justification

Flexible Quadrat

To calculate the area cover of Trentepholia aurea at each aspect of the tree

The flexibility allows you to calculate the most accurate area of Trentepholia aurea growth on each oak tree

Tape Measure

To ensure the height the Trentepholia aurea is measured at remains consistent

Gives an accurate and equal level at which can easily be measured on every tree.

Compass

To accurately find each aspect of the tree

Easy to use and gives the best indication as to the aspect

Thermometer

For surrounding temperature measurements.

As temperature is a control, it is just to be monitored. A thermometer is sufficient to do so and will also give accurate results.

Light meter

To record the light levels at every 4th reading.

The light, also a control, is just to be monitored. The light meter gives a very accurate reading and will ensure reliability of results.

Trial Method:

Site area: Rushey plain
Using a compass, find the north side of the oak tree.
Measure 1.5 metres up the oak tree from the base and line up the bottom of the quadrat.
Place the quadrat flat on the bark of the oak tree.
Roughly calculate the area the Trentepholia aurea fills and record your results.
Repeat this for the south, east and west sides of the tree.
Continue collecting results until you have enough data.
Preliminary Results:

Aspect

North (%)

East (%)

South (%)

West (%)

Tree 1

75

12

2

46

Tree 2

70

31

6

34

Tree 3

60

26

14

60

Tree 4

20

0

9

46

Tree 5

20

17

3

0

Tree 6

28

8

6

18

Tree 7

27

1

0

7

I found that there was a clear correlation between Trentepholia aurea growth and aspect of the tree, with the Trentepholia aurea growing more on the north side of the oak tree.

I have chosen to investigate this further in my final study.

Amendments:

I found that there was no evidence of control recordings, and when I stepped back onto the path I could not remember which of the oak trees with Trentepholia aurea on I had already recorded.

In order to incorporate this into my investigation I will record temperature of the surrounding area and light intensity at every forth data reading.

I will also ensure that I tie a piece of wool around each tree that I take recordings from.

To carry out a Mann-Whitney U-Test I will need to take a larger number of samples, so I will aim to take 20 in my study.