Practical - Factors affecting abundance and distribution of a species

Greg Foot describes how to carry out a field investigation into distribution and abundance of organisms in an ecosystem

Aim

To measure the species richness on the school field in areas in which the grass is regularly and irregularly cut.

Method

  1. Choose a starting point on the school field in an area where the grass is often cut.
  2. Use random numbers to generate a set of coordinates to place your first quadrat.
  3. Count the number of different plant species within this quadrat (the species richness).
  4. Return to your starting position and repeat steps two and three a further 14 times using different random numbers.
  5. Repeat steps one to four for a part of the school field where the grass is infrequently cut.
  6. Compare your results by calculating a mean for each location.
Question

What are the totals and means for the two different locations?

Quadrat number123456789101112131415
Number of plant species per quadrat on cut area of the school field121231311123211
Number of plant species per quadrat on uncut area of the school field324611145364534

A total of 25 and a mean of 1.7 on cut school field and a total of 52 and a mean of 3.5 on uncut school fields.

Question

What conclusions can you draw here? [4 marks]

The mean of the number of plant species in the cut school field is lower than on the uncut school field (1 mark). There is a mean of 1.7 different species per quadrat on the cut grass (1 mark). The number of plant species per quadrat on the uncut field is over twice this at 3.5 (1 mark). Therefore, there is greater species richness on the school field in uncut areas (1 mark).

Question

What limitations might there be in drawing these conclusions?

In this example, the students only placed 15 quadrats. Completing more would allow them to be more confident in their conclusions.