Population Distribution and Abundance

• Organisms distribute themselves within an ecosystem in three patterns:
  • Clumped: Individuals group in patches.
  • Random: Individuals spread unpredictably.
  • Uniform: Individuals are evenly spaced.

Measuring Abundance (Population Size) via

• Direct Observation
  • Sighting involves observing and recording the number of individuals.
  • Counting involves actively counting individuals.
  • Sampling a population involves taking a small sample to estimate the total population.
• Quadrat Sampling
  • Place square frame quadrats randomly or systematically.
  • Count the number of individuals of each species within the quadrat.
  • Repeat the process across multiple quadrats.
• Transect Sampling
  • Observations/measurements occur along a straight line across a habitat.
  • Useful for studying changes in vegetation or species distribution along an environmental gradient.
• Capture-Recapture Method
  • Capture, tag, and release a sample of individuals.
  • Capture a second sample after allowing time for mixing.
  • Count tagged individuals in the second sample.

3Rs For All Population Techniques

• Replacement: look for alternatives to using animals.
• Reduction: Reduce the use of animals to as low a level as statistically necessary.
• Refinement: Decrease inhumane practices where possible.

Capture/Release Method Advantages

• Accurate for mobile species in a defined area
• All individuals do not need counting
• Animals are not hurt when captured and released though they may be stressed
• Allows for extended analysis if the population is sampled over a long time

Disadvantages

• Equal chance of animal’s capture is not a given, which may cause inaccuracy
• Some could be 'trap happy' and sampled a lot because they are curious
• Marked animals could disappear/move or even die

Western Shield

• Focuses on protecting and recovering native wildlife populations.
• Achieved by controlling introduced predators like foxes and feral cats.
• Uses baiting with 1080 poison, habitat restoration, and monitoring techniques.

1080 Baiting

• Pest control using sodium fluoroacetate (1080), a highly toxic compound.
• Disrupts cellular energy production by interfering with the Krebs cycle.
• Converted into fluorocitrate, which blocks enzymes and stops cells from producing energy.
• Animals suffer heart or respiratory failure, usually within hours.
• Manages invasive pests like foxes, wild dogs, feral cats, possums, and rats.
• Protects native wildlife, agriculture, and livestock.
• The poison is used in meat, cereal pellets, or carrots.
• Deployed via ground baiting or aerial drops.
• Controversial due to high toxicity to domestic animals, risks to non-target wildlife, and animal welfare concerns.

Monitoring Techniques

• Sheffield traps are small metal cages to trap animals for monitoring and research
  • Used to assess population health.
  • Help identify species.
  • Assist in monitoring reintroduced species.
• Non-Invasive monitoring methods
  • Motion sensor cameras.
  • Poo and DNA samples.
  • Tracks and footprints.
  • Acoustic monitoring.

Dieback

• Disease that cuts off plant water supplies and lives in the soil.
• Control measures:
  • Dieback hygiene stations for cleaning boots, vehicles, and equipment.
  • Track and road closures.
  • Chemical treatments.
  • Mapping and monitoring.

Fire Adaptations

• Fire can cause succession allowing a community to move on from a primary succession to a secondary one.
• Fire alters the structure of a community.
• Frequency and intensity can change the composition of species.
• In Tasmania, vegetation depends on fire frequency:
  • Frequent fires favor fire-resistant shrubs.
  • Less frequent fires allow more eucalyptus trees to grow.
• Adaptations include specialized structures or processes for survival and regeneration.

Adaptations

• Fire resistance:
  • Some trees have thick bark for protection.
  • Tall trees may have canopies spared from less intense fires.
• Epicormic buds:
  • Native trees have epicormic buds underneath the bark.
  • Fire causes new growth using these buds after leaves and arms have been burnt.
• Lignotubers:
  • Swelling at the base of the plant contains dormant buds.
  • After a fire, buds activate, and the plant regenerates.
• Fire-activated seeds:
  • Seeds have a hard resin coating activated by fire.
  • Fire cracks the coat for water to enter which allows germination to occur.
  • Seeds germinate in ash, high in nutrients and low in competition.
• Grass trees:
  • Dead leaves form insulation, are resistant to the fire’s heat.
  • Living growth point is underground and protected.
  • Flower after a fire to take advantage of nutrient-rich soil.

Differences In Fires

• Prescribed fires:
• WA implements a rigid fire management program to reduce the risk of catastrophic bushfires
• Perth neighbors are dense bushland that can become a site of a catastrophic bushfire if not managed.
• Perth hills:
  • They have lateritic soil that holds minimal water and is low in nutrients.
  • This leads to dry land, contributing to bushfires.
  • Risk increased due to topography and proximity to the ocean.
  • Fires spread fastest uphill.
  • Windy conditions increase fire spread.

Fuel Load

• Prescribed fires reduce fuel load.
• Dry leaves and branches are flammable and worsen fires.

Prescribed vs Bush Fire

• Prescribed fires:
  • Burned areas are patchy.
  • There is a lower intensity as trees are still standing with only lower trucks being burnt
  • Only consumers leaf litter and undergrowth rather than trees
• Bush fires:
  • Widespread and intense burning, large areas are blackened
  • Trees scorched and even collapsed and turned to ash
  • Penetrate deep in the soil, killing plant roots which makes regeneration slower.

Bush Fire Frequency and Intensity

• Over the last 200 years, the frequency has decreased.
• The bushfires that do occur become more intense and have greater risk to the ecosystem and humans
• Increasingly warmer climate is increasing the risk of catastrophic bushfires.
• Longer and hotter summers increase fuel load, leading to higher intensity fires.