Techniques for studying ecosystems

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A quadrat is a sqaure frame used for studying ecosystems. 

  • It is used to study the abundance and distribution of different plant species
  • Some plants are difficult to count as individuals so percentage cover is used instead

Some precautions must be taken:

  • Randomly position the quadrats across the habitat, using random numbers to plot coordinates.
  • You need your sample size to be large enough. Ecologists create a cumulative frequency table. When the graph levels off, you know that your sample size is large enough.

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Population size of a species

Population size of a species = 

Mean number of individuals of the species in each quadrat 


Fraction of the total habitat area covered by a quadrat

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  • These help you to look more systematically for changes in vegetation in a habitat.
  • A transect is a line taken across the habitat.
  • This line is usually created using a tape measure.
  •  Samples are taken at random intervals.

There are two approaches to taking a transect:

  • Line transect - at regular intervals, take note of the species touching the tape measure.
  • Belt transect - at regular intervals, place a quadrat next to the line or move the quadrat along the line to get a more accurate representation of the habitat.
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