Succession

• Describe primary succession

  • Pioneer species (first species to colonise an area)
  • Colonise bare rock
  • Seeds/Spores blown in by wind + grow
  • Harsh abiotic conditions (soil has low H2O retention)
  • Pioneer species specially adapted
  • They change the abiotic conditions less hostile (break rock, die, add dead organic matter (humus) as they decompose)
  • Now soil can retain H2O
  • So new organisms can colonise + die
  • Increasing organic material of soil
  • New species change environment
  • Less suitable for previous species
  • Previous species outcompeted by larger plants
• Describe secondary/tertiary succession

  • Already soil present
  • So pioneers are larger plants
  • Climax reached quicker (as succession starts at later stage)
  • At each stage, better adapted organisms move in + outcompete prior organisms
  • Become dominant species
  • Till a stable climax community is reached