Succession

• Succession is the process by which an ecosystem changes over time. The biotic conditions change as the abiotic conditions change.
• Primary Succession - This happens on a land that has been newly formed or exposed such as where a volcano has exploded to form a new rock surface - There is no organic material to start with.
• Secondary succession - This happens on land that has been cleared of all the plants, but where the soil remains such as after a forest fire.
• Primary succession starts when a species colonise a new land surface. Seeds and spores are blown by the wind and begin to grow.
• The first species to colonise an area are called pioneer species
• The abiotic conditions of a new area are hostile. Only pioneer species grow because they are specialised to cope with the harsh conditions.
• The pioneer species causes a change in abiotic conditions - they die and microorganisms decompose the dead organic material to form basic soil.
• The formation of soil makes the conditions less hostile and can help to retain water, which means new organisms can more in and grow. These die and are decomposed, adding more organic material, making the soil deeper and richer in minerals.
• Secondary succession is similar to primary succession, but becuase there is already a soil layer succession starts at a later stage. The pioneer species in this is larger plants.