succession

• Primary succession involves the changes from pioneer species which colonise an environment

  Changes in abiotic factors lead to more favourable conditions and increasing species diversity
• primary succession Begins in a place without any soil

  Sides of volcanoes

  Landslides

  Flooding

  Starts with the arrival of living things such as lichens that do not need soil to survive

  Called pioneer species
• Features of pioneer species -

  • Can tolerate extreme conditions e.g. low nutrient levels
  • Have very good means of dispersal, usually by wind
  • Are not able to compete for resources e.g. light
  • Are not influenced by or dependent on animal species
  • May be able to fix nitrogen (e.g. legumes) and build up soil nutrients
• primary succesion -

  • Soil starts to form as lichens and the forces of weather and erosion help break down rocks into smaller pieces
  • When lichens die, they decompose, adding small amounts of organic matter (humus – not the chickpea dip ) to the rock to make soil
• climax community -

  • A stable group of plants and animals that is the end result of the succession process
  • The climax community produced is controlled by the climate.
  • Eg. water present all year – generally woodland
  • distinct wet and dry seasons – grassland
  • wet and acidic – blanket bog
  • Does not always mean big trees
• secondary succession -

  • Begins in a place that already has soil and was once the home of living organisms
  • Occurs faster and has different pioneer species than primary succession
  • Example:  After forest fires, human activity
• • The succession process is altered, this is called deflected succession
  • Types of activity that can interrupt succession include: deforestation; ploughing; grazing; water drainage; weeding/coppicing; introducing new species.
• • Plagioclimaxes are what is produced at the end of a deflected succession.
  • Most habitats in the UK are plagioclimaxes produced by grazing, burning, mowing or cutting.
  • Examples include grassland and heathlands which are used of agriculture
  • Coppiced woodlands