National Parks & Biodiversity on Paths
Stage 4: Handling and analysing the results.
Discussion about the two different methods:
- If you haven't already done so look at the raw results from the investigation in these Excel files -
- Note that the base line of the point sampled transect was the edge of the belt transect.
- By looking at the data and graphs carefully you can see the following pros and cons of each method.
Comparison point | Belt transect | Line transect |
|---|
Time for collecting
the sample | Slow – transect takes 60mins
- can only do a few samples which may give a false impression. | Very quick – 15 minutes
- can do lots of samples at different points on the path – may give a better indication of what is going on. |
Vegetation height | Good profile which shows the change across the path, but only 1 measurement per metre.
Gives a better indication of height as it is maximum height for the 0.5m quadrat.
- the profile gave a more realistic representation of vegetation height. | Profile will depend on where the line goes. Could give a false indication if it misses the bulk of the vegetation.
Is sampled every 25 cms.
- the line passed through the transect avoiding much of the dense vegetation – not a realistic indication. |
Number of species –
an indication of
biodiversity. | Gives an accurate indication of species present and how they change across the path.
- does not miss species. | Very easy to carry out but it missed a few species.
- could miss a rare and important species. Possibly get over this by doing repeats. |
% cover | Gives a reasonably accurate idea of how abundant the plants species are.
- shows effects of the path very clearly. A major advantage of this method. | No indication of changes in abundancy across the transect.
- a major disadvantage in assessing change across the path. |
% cover for grass | Although no grass species were identified, graphs clearly show a change in abundancy of the grass across the transect.
- some grass species are path tolerant and can indicate change. | Does not show how grass is being affected.
- could get over this by recording the species of grass – some species are path tolerant and their distribution would indicate change. |
Our conclusions:
The line transect with point sampling was very quick and allowed for a much better sample at a number of different points up and down the path. But it did miss some species (although this could have been overcome by an increase in the number of samples), and it also gives no indication of abundancy of plant species across the path.
Height profiles are clearer using the belt transect as they record the highest plant in each quadrat, which gives a better indication of the plant density.
The major advantage of the belt transect is the percentage cover data, which gives a good indication of how abundant certain plants are.
On balance, even though it takes more time, the belt transect is the most suitable method for this investigation. It produces data which will show how the path is affecting the plant species number, distribution and density.
What improvements to the investigation can you think of?
- How many transects?
Do a total of 3 belt transects.
- What about a control?
Do a transect across an area that has no path as a
control.
- What kinds of grass are there?
Identify the different species of grass –
look for grass species which are path tolerant.
- How will path slope affect the investigation?
Map a profile of the path and relate slope and
depth to the transect.
Using the results
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Hay Tor sample data - belt transect
Erosion graphs
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