Sampling

• Biodiversity


  The variety of life within and between organisms
• Measuring biodiversity


  • Challenging
  • Requires identification and cataloguing of all organisms present to build a species list
  • Impossible for larger and more complex ecosystems like rainforests
• Sampling to estimate total species numbers

  1. Take different samples of the area

  2. Use the samples to make an estimate for the total species numbers in the area
• Random sampling


  Positions of the sampling points are completely random or due to chance
• Non-random sampling


  Positions of the sampling points are chosen by the person carrying out the sampling
• Random sampling


  • No bias by the person carrying out the sampling
  • Best choice when the sampling area is reasonably uniform or has no clear pattern to the way the species are distributed
• Quadrats


  Square frames made of wood or wire used to mark off the areas being sampled
• Using quadrats for sampling

  1. Place quadrats randomly in the area

  2. Record the abundance or percentage cover of all the different species present within the quadrat
• Opportunistic sampling


  Picking and choosing sampling locations based on various non-random factors
• Stratified sampling


  Matching the number of sampling locations in a particular habitat with the relative proportion of area that habitat covers in the whole area being studied
• Systematic sampling


  Used when there is a clear change in the physical conditions across the area being studied
• Line transect


  1. Lay out a measuring tape in a straight line across the sample area

  2. At equal distances along the tape, record the identity of the organisms that touch the line
• Belt transect


  1. Place quadrats at regular intervals along the tape

  2. Record the abundance or percentage cover of each species within each quadrat