Sampling Ecosystems

Sampling, Quadrats, Transects

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Sampling Key Terms

Sampling:- selecting small porrtinos of the habitat to find out the abundance and distribution of species and any environmental factors

Distribution of species - presence or absenc of each species

Abundance of species - the number of individuals of each species

Species Frequency - the proportion of quadrats with a parituclar species in it

Percentage Cover - using a gridded frame quadrat; the smaller square the more accurate

 Population size= mean number of individuals in each quadrat/fraction of the total habitat covered by quadrats

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Quicker than counting but accuracy only improves through practice. Uses the ACFOR Scale - Abundant, Common, Frequent, Occasional, Rare (DAFOR - Dominant, Abundant)

Point Frames:- used to make more accurate percentage cover estimates. It has 10 pins, each representing 1%. Lower the pins to the ground and record each species in contact with the tip of the pin as it is lowered - repeat 10 times per quadrat

Avoiding Biased Random Sampling

  • Use random number generators to select coordiantes to place a a quadrat - found along two perpendicular tape measures
  • Record the Distribution or Abundance of species in the quadrat - repeat 3 times and calculate the mean (inlcuding anomalies)

How many quadrats and how big:

  • take random samples across the habitat and make a cumulative frequency graph - where this plateaus, is the minimum number of quadrats to use
  • Repeat this using larger and larger quadrats to calculate the optimum size
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Line Transects:- used for habitats with gradations (sand dunes). Tape meausre placed across the gradation at right angles from sea to high tide zone for example

All specis touching the tape meausre are recorded and so is their postion

Belt Transects:- wider than line transects as quarats are place along the tape

  • Continuous belt transects - no spaces between each quadrat sample
  • Interrupted belt transects - regular intervals between quadrat samples
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