Barcelona Field Studies Centre

Optimum Quadrat Size Sampling Technique

The optimum quadrat size sampling technique maximises the accuracy of the data recorded balanced against the time and effort required to collect it.


Optimum quadrat size species-area curve

The species-area curve shown above is produced by counting the number of different species types in a quadrat. The optimum sampling size of 4m2 is shown in red, where a further doubling of the quadrat size has an insignificant effect on the number of new species recorded. The optimal quadrat size selected is the lowest size returning maximum information in the time available.


Method

  1. Count and record the number of different plant species within a 0.25m2 quadrat.
  2. Double the quadrat area to 0.5m2 and count the number of new species found. Add this number to the total.
  3. If no new species are found, 0.5m2 is the optimal quadrat size.
  4. If new species are found, repeat the process by doubling the quadrat size until no new species appear.
  5. When no new species are found, record the total and the optimum quadrat size used to collect the data.