Changes in Ecosystems

• Ecological succession


  Succession is a process of change in community composition and structure, usually towards the establishment of a stable ecosystem. It includes changes in both the biotic and abiotic factors in an ecosystem over time. When a stable community is established, it is known as a climax community.
• Primary succession


  Begins in a barren area with no soil
• Secondary succession


  Begins in an established area with soil
• Primary succession


  Begins with a new area with no life, barren

  There is no soil to begin with

  Pioneer plants such as lichen

  Lower productivity due to fewer plants

  Low biodiversity for a long time
• Secondary succession


  Begins with the disturbance of an already established ecosystem and it begins after a primary succession.

  Soil is present at the beginning

  Seed and roots of established vegetation are already present

  Higher productivity due to there being more plants and faster growth

  Faster development of wider biodiversity
• Example of secondary succession

  Australian bushfires. Scientists across the country study the regeneration of ecosystems post-fire.
• Climax community


  is the stable community present at the final stage in a succession. It is stable as long as environmental factors remain unchanged. Such communities tend to be made up of slow-growing, long-lived K-selected species. These species, living in more stable environments than r-selected species, out-compete the others around them.
• Natural disturbances can cause succession

  Erupting volcanoes

  Fire

  Tsunamis

  Flooding
• Fire


  Can have varied effects on ecosystems
• Fire intensities


  • Depend upon weather
  • Depend upon fuel load
• Rate of spread of a fire

  1. Affected by wind speed

  2. Affected by moisture content of the fuel

  3. Affected by fuel particle size

  4. Affected by vegetation height

  5. Affected by fuel bulk density

  6. Affected by percentage of dead fuels

  7. Affected by topography
• Immediate negative effects of fire on the biota of a community

  • Loss of vegetation
  • Reduction of leaf litter
  • Increase in animal suffering
  • Decrease in animal numbers
• Degree to which fire changes the populations of species present in a habitat

  • Depends on the kind of fire (canopy, understorey or both)
  • Depends on the intensity of the fire
  • Depends on the scope of the fire
• Benefits of fire


  • Removes the slow-growing but dominant trees and shrubs, thereby opening up space for other living things (e.g. herbaceous, grass-like species) to come
  • Returns nutrients to the soil that were previously locked up in plant biomass
  • The heat of the fire can lead to biotic changes, because some species of bottlebrushes, hakeas, some acacias and eucalypts regenerate from fire-released seeds
• Benefits of smoke


  Germination of species which are difficult to germinate by other means

  More uniform and earlier germination

  Seedlings which are more robust
• Fire regimes


  Long-term changes in an ecosystem can result from sequences of fires known as fire regimes.
• Fire regimes determined by:

  •the season in which fires occur

  •the intensity of the fires•

  most importantly, how frequently the fires occur.
• Eucalypts, acacias and shrubs that make up the unique Australian landscape thrive in the natural fires of lower intensity and frequency.
• Fire is rapid and dramatic, but even though it changes ecosystems, the original ecosystem can potentially be re-established over many years by succession.
• Ecosystem change 


  Australia experiences daily and seasonal changes, which are examples of relatively short-term change. But over the last 15 million years, there have also been major long-term changes to ecosystems in Australia.

  These include the expansion of desert in central Australia, which has replaced the inland seas and tropical ecosystems that once existed. The desert ecosystems are still changing, becoming increasingly arid.

  The Cockburn Range, like other ecosystems, is always changing. It was once a lush rainforest and now it is a tropical savannah.
• Primary succession following glacier retreat

  1. Bare rock left after glacial retreat

  2. Mosses and lichen start to colonise the rock

  3. Organic matter added to weathered rock particles, making simple soils

  4. Grasses and small herbaceous plants start to grow

  5. More organic matter added, roots of plants aid break up in rock material

  6. Deeper soils hold more water, small shrubs colonise these better soils

  7. Nutrient availability increase so there is more root action

  8. Trees establish, leading to a development of a climax community on mature soils
• Fire regimes 


  Traditionally, Aboriginal and Torres Strait Islander People regularly burned sections of the bush to aid hunting and stimulate new growth of plants for food. So-called ‘fire-stick farming’ greatly increased the frequency of fires in many parts of Australia and gave rise to a pattern of vegetation that became dependent on regular burning. This human intervention disrupted regular succession patterns to maintain a grassland state.
• Throughout much of Australia, Indigenous Australians changed the existing regime of fire induced by lightning to one of fire induced by humans, so they could manage and sustain the productivity of the land.

  In the process, the distribution and abundance of plant species changed, and those that were more fire-tolerant increased.

  This in turn produced changes in the distribution and abundance of wildlife.
• Technology to improve monitoring of change

  Contemporary technologies such as drones and GPS can help collect data and monitor the activities of animals and animals more accurately.

  These technologies are currently used by different groups to restore environments. For example, the WA Department of Biodiversity Conservation and Attractions uses these technologies to restore Dirk Hartog Island (Wirruwana) to its pre-settlement ecosystem.
• If the prescribed burning rate is faster than the plant life cycle then plant species will start to disappear
• Plants that have a juvenile period of more than 6 years

  • Banksia baueri
  • B. nutans
  • B. baxteri
• Banksia baueri, B. nutans and B. baxteri


  • Keystone, nectar-producing species
• Banksia baueri, B. nutans and B. baxteri would gradually be eliminated
• Species associated with late stages in the series or climax states of the ecosystem

  • tammar wallabies
  • quokkas
  • honey possums
• Species associated with late stages in the series or climax states of the ecosystem would disappear
• To protect the biodiversity of the southwestern area of WA, careful consideration of the life cycles and impacts on the plant and animal life is required
• Projections of climate change suggest there will be more frequent and intense fires in the future
• It is imperative that scientists find out the best strategy for long term protection of our unique biodiversity
• Mining and ecological restoration


  Mining has resulted in economic benefit but also devastated many habitats, so restoration plans are required when mining sites are established
• WA's mining boom has resulted in huge economic benefit to all Australians
• Mining blasting and digging has enormously changed the landscape, devastating many habitats
• Eventually government enforced restrictions on mining development and when mining sites are allowed to be established, a restoration plan is required for the surrounding ecosystems
• Koolanooka Mine Site


  400 km NE of Perth, in the process of being restored
• The use of research provided effective ecological restoration of vegetation communities at Koolanooka, Blue Hills and Weld Range, which have been or will be impacted by iron-ore mining
• The mine aims to restore 70 per cent of the known original species diversity