Sampling techniques

• Uniform distribution


  Organism can be territorial
• Random distribution


  No clear pattern, individual organisms do not interact strongly with each other
• Clumped distribution


  Definite patches, may be due to resources
• Total counts


  Involves counting each individual in a population, only works on particular species
• Sampling techniques


  • Used when total counts are not practical
• Stationary organisms - Quadrats


  Quadrats and transects are used, quadrats are areas of known size often subdivided into smaller units, number of plants are recorded
• Abundance


  138 plants in 10 one metre^2 quadrats, the abundance is 13.8 plants per square metre
• Critical factors to take into account for quadrats

  • Size of the quadrat, number of quadrats, sampling sites are selected randomly and objectively
• Stationary organisms - Transects


  Transects measure the distribution of the organism, line or strip laid across an area, at fixed intervals changes in vegetation are recorded
• Mobile organisms


  The formula is applied: p= (a x n)/r, where p = estimated population size, a = number of marked animals released, n = total number of animals recaptured, r = number of marked animals recaptured in the sample
• Limitations of capture-recapture method

  • The released animals do not mix at random with the rest of the population, animals migrate into or from the area over the period of the study
• Glossary Terms


  • Abundance
  • Distribution
  • Quadrat
  • Transect
  • Capture-recapture