Ecological succession
= A natural and predictable pattern of gradual change over time in the types of species in a
community following a disturbance.
e.g. Knysna Fires = ecologists new what would happen in each environment.
Our indigenous forests barely burnt as they are so wet, have a canopy, keep moisture in.
Open fynbos and alien species = burnt easily and the alien vegetation spread seeds.
Type 1: Primary succession
Begins on sites that have not previously had plants growing on them (no soil before)
Examples: beaches, larva flows, severe landslips and bare rock.
Type 2: Secondary succession
Begins in areas where there is a disturbance that removes some or all of the species, but the
soil remans.
Community structure
Is not static, but it determined over time by succession that takes place as a result of:
- Disturbances
. a. Caused by physical disasters, such as storms, floods, fires.
. b. Caused by humans or animals, such as abandoned crop fields, overgrazing, logged area.
. c. Caused by climate change.
- Competitive interactions
Stages in succession
Order of change is not random.
Communities initially have a small number of simple species which are gradually replaces by a
large number of complex species.
Stage 1: Pioneer species
= first species to colonise an area
Bare ground favours pioneer plant species.
These species grow best where there is little competition.
Features:
- Are able to withstand extreme variations in climate
- Establish rapidly as they have shallow roots
- Have spores or seeds and are light
- Do not grow in the shade
Pioneer species prepare the surroundings for later colonists by altering the biotic and abiotic
environment.
They do this by:
- Building up, stabilising and enriching the soil
- Altering the amount of light available by providing shade
= A natural and predictable pattern of gradual change over time in the types of species in a
community following a disturbance.
e.g. Knysna Fires = ecologists new what would happen in each environment.
Our indigenous forests barely burnt as they are so wet, have a canopy, keep moisture in.
Open fynbos and alien species = burnt easily and the alien vegetation spread seeds.
Type 1: Primary succession
Begins on sites that have not previously had plants growing on them (no soil before)
Examples: beaches, larva flows, severe landslips and bare rock.
Type 2: Secondary succession
Begins in areas where there is a disturbance that removes some or all of the species, but the
soil remans.
Community structure
Is not static, but it determined over time by succession that takes place as a result of:
- Disturbances
. a. Caused by physical disasters, such as storms, floods, fires.
. b. Caused by humans or animals, such as abandoned crop fields, overgrazing, logged area.
. c. Caused by climate change.
- Competitive interactions
Stages in succession
Order of change is not random.
Communities initially have a small number of simple species which are gradually replaces by a
large number of complex species.
Stage 1: Pioneer species
= first species to colonise an area
Bare ground favours pioneer plant species.
These species grow best where there is little competition.
Features:
- Are able to withstand extreme variations in climate
- Establish rapidly as they have shallow roots
- Have spores or seeds and are light
- Do not grow in the shade
Pioneer species prepare the surroundings for later colonists by altering the biotic and abiotic
environment.
They do this by:
- Building up, stabilising and enriching the soil
- Altering the amount of light available by providing shade
