Sampling technique

• what problems can random sampling cause?

  • missing out less common/rare plant species
  • visual survey should be taken and the rarer species recorded as present, but with no abundance - meaning they can't be used in statistical analysis
• what is the method of the abundance scale?

  • abundance is ranked into categories
  • most common is the ACFOR scale:
  • Abundant
  • Common
  • Frequent
  • Obvious
  • Rare
• what is the method of density for estimating plant abundance?

  • for large plants that can be seen individually, count the number of individuals in a 1m by 1m quadrat
  • gives density per square meter
  • this is an absolute measure, not an estimate
• what is estimating frequency as a method of measuring plant abundance?

  • for plants that are too small to count individually
  • count number of small squares of the quadrat the plant is present in
  • if there are 100 squares - each square is 1%
  • if there are 25 squares - each square is 4%
• what are problems with sampling animals?

  • animals move - could be sampled twice or missed altogether
  • animals are disturbed if they are aware of the presence of humans
• how should you sample small animals?

  • should be caught/trapped - use this to estimate population size
• how should you sample large animals?

  • not trap
  • use of hides
  • using droppings to identify presence
  • other signs such as deer damaging tree bark or rabbit burrows
• how do you use quadrats when sampling animals?

  • used to sample animals such as barnacles, muscles or sea anemones
  • divide area into a grid
  • use a random number generator to produce coordinates
  • count number of individuals, or estimate percentage cover in each quadrat
• how do you use sweep netting when sampling animals?

  • insects
  • sweep net through vegetation in wide areas
  • net emptied onto white sheet and use a pooter to collect insects before they crawl/fly away so you can identify them
  • suitable for low vegetation that isn't woody
  • may scare away large animals
• how do you use pitfall traps to sample animals?

  • bury a small container in the soil/just below surface
  • small animals moving through plants will fall in and are trapped
  • trap should be sheltered when raining to prevent flooding
  • cheap
  • simple procedure
  • can harm insects (eating each other e.g.)
• how can tree beating be used to sample animals?

  • spread a white sheet below a brand
  • beat branch with a stout stick to dislodge any animals
  • use a pooter to identify
  • quick
  • white sheet allows for easy identification
  • species stuck inside tree won't be identified
  • may damage tree
  • insects may crawl away before identification
• how can kick sampling be used to sample animals?

  • river bank/bed is disturbed with a kicking action for a set period of time
  • a net is held just downstream for a set period of time to capture any organisms released in the flowing river
  • empty net contents into a tray containing river water
• how can tullgren funnel be used to sample animals?

  • leaf litter placed in funnel - a light above drives the animals downwards (leaf litter dries out and arms up) through a mesh into a container below
  • randomly chose location to avoid bias
  • ethanol could kill
  • water could drown
• how are light traps used to sample animals?

  • an ultraviolet light attracts the insects, which fall into a vessel
  • containing alcohol vapour which sedates they
  • cost effective
  • easily repeated
  • less productive when wet, cold, windy
• what are biotic factors?


  the living components of an ecosystem
• what are abiotic factors?

  the non-living components of an ecosystem
• what are the advantages of measuring abiotic factors with sensors?

  • rapid changes can be detected
  • human error in taking a reading is reduced
  • a high degree of precision can often be achieved
  • data can be stored and tracked on a computer
• what does Simpson's index of diversity take into account?

  • species richness
  • species evenness
• what is Simpsons Index of Diversity?

  D = 1 - E(n/N)2

  always between 0 and 1
• what are biotic factors?


  the living components of an ecosystem
• what are abiotic factors?

  the non-living components of an ecosystem