Ecology of a habitat

Various abiotic factors that affect the abundance of the distribution of a certain species can be

investigated in this ecological study. Some examples include:

• Light intensity (e.g. area in shade or in sunlight)
• Distance from a large tree / river / lake / path
• River depth
• Area - woodland, heath or grassland

Equipment list

• 0.25 m2 quadrat with grid
• 20 m belt transect
• Clipboard and pen
• Identification book
• Measuring equipment depending on the factor being investigated - for instance a light

sensor

Method

When carrying out an ecological study of a habitat there are 2 main methods of sampling:

1. Transects - this samples across an area and measures an environmental gradient

2. Quadrats - this samples at 2 environmentally different areas

Method 1 - Quadrats

1. Draw a large grid over the images or maps of the 2/3 areas being sampled at. Assign a

numerical scale to the grid, creating a coordinate grid.

2. Use a random number generator to generate 20 coordinates for the first area, these will

be where the quadrats are placed.

3. Place a quadrat at the generated coordinates and count the number of the species being

investigated in the quadrat, or the percentage cover. If a box of the quadrat is more than

half-filled by the species being investigated, count that as a full box and then calculate the

percentage of full boxes counted. If investigating small species, or species that are hard

to distinguish from each other then percentage cover is the most practical way to measure

abundance; whereas if investigating a species like daisies where they are easy to count

then record species frequency. Record

the abundance in a suitable table.

4. Repeat step 3 with the remaining 19 quadrat sampling locations.

5. Repeat steps 2-5 in the other sampling areas.

Method 2 - transect

1. Choose an area with a clear environmental gradient in the abiotic factor being

investigated - for instance under a tree where it is shaded, out into the open where there is

no shade.

2. Lay the belt transect across the gradient, starting in the shaded area. Place the quadrat at

the 0m mark and count the number of the species being investigated in the quadrat, or the

percentage cover, recording the results in a suitable table. Also take a measurement of the

independent variable being investigated, in this case use the light sensor and record a

reading of the light intensity.

3. Repeat step 2, placing the quadrat every 2 metres down the transect to take samples so

you have taken 10 across the 20m line.

4. Repeat steps 1-3 in different areas at the site with the same environmental gradient being

investigated. This means you end up with multiple results for each distance.

Results table

Method 1 - quadrats

Method 2 - transects

Analysis

After the experiment and data collection you can carry out a statistical test to examine whether

the results you obtained are significant. It can also be used to reject or accept a null hypothesis.

Transect experiment

Use a spearman’s rank correlation coefficient test to determine whether there is a correlation

between the independent and dependent variable and whether the correlation is significant or not.

Quadrat experiment

After the experiment, exclude anomalous results and calculate a mean percentage cover or

frequency for each area, these can be statistically compared using the student’s t-test which

determines whether or not there is a significant difference between the means of 2 or more areas.