Experimental Methods Using Quadrats and Transects

Organization of an Ecosystem

• Feeding relationships in an ecosystem can be observed in food chains.
• Sampling allows measurement of abundance and distribution of species.
• Essential for monitoring conservation projects targeting endangered species or habitats.
• Full population counts are often impractical, thus sampling small sections is used.

Sampling

• Involves counting organisms within a sample site, then estimating total numbers in a habitat.
• Large animals/plants can often be counted directly.
• Smaller animals may need to be trapped first (e.g., using pitfall traps).
• Methods include:
  • Pitfall traps: Small traps in the ground to capture small mammals.
  • Sweep netting: Using nets to sweep through grasses or leaves.
  • Kick-sampling: Nets downstream in a river to catch aquatic organisms.
  • Pooters: Devices to suck up small insects safely.

Using Quadrats

• Quadrats are square frames (usually 0.25 m²) placed on the ground.
• Used to study plants or slow-moving animals.
• Sampling methods include:
  1. Number of individual species (e.g., counting daisies).
  2. Species richness (number of different species).
  3. Percentage cover (e.g., amount of area covered by grass).
• Random or systematic placement of quadrats used for sampling.

Random vs Systematic Sampling

• Random Sampling:
  • Placing quadrats at random coordinates.
• Systematic Sampling:
  • Used when there is a trend/pattern, e.g., along a beach or hillside.
  • Ensures unbiased results.

What Are We Sampling For?

• To observe changes in species number or percentage cover due to abiotic factors.
• Example: Investigating seaweed growth related to tidal distance.
• Utilizes systematic sampling along a transect.

Transects

• A transect is an imaginary line across a habitat.
• Quadrats placed at regular distances along transect (e.g., every 5 meters).
• Used to link changes in species to abiotic factors.

Zonations

• Change in species distribution across a habitat is called zonation.
• Example: Change in dandelion plant distribution along a transect.

Kite Diagrams

• Results from transects can be visualized as kite diagrams.
• Width of bar indicates number of individuals at a point.

Additional Notes

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