Changing Ecosystems
Primary vs Secondary Succession
Primary succession
Starts from bare rock or water.
Occurs in an environment that is devoid of vegetation, organisms and soil (such as a lava
flow or area left from retreated glacier).
Basically, it’s the gradual growth of an ecosystem over time.
Secondary Secession
Starts where there has been vegetation before.
, What is succession?
Is the process of gradual changes in an ecological community over a period of time. These changes
are orderly and generally predictable in the absence of major disturbances.
Primary Succession
Stage 1
Pioneer species are the first species to colonise an area, and tend to be lichen
o They are opportunistic species which are able to rapidly exploit a sudden new opening in
ground plant cover.
o They are able to withstand desiccation, extremes of temperature and low levels of nutrients.
o They must be able to grow quickly, but are usually short lived.
Stage 2
The pioneer species penetrate and break up the rock.
o As they die and decompose, humus builds up.
o This allows other simple plants such as mosses and ferns to now grow.
Stage 3
Mosses and ferns cast shade to stop further growth of lichens
o Their roots are longer and so further break up the rock.
o The organic matter gradually increases as these bigger plants die. More water is retained by
this, so grasses, small flowering plants and shrubs can grow.
Stage 4
Growth of larger plants and the animals which inhabit them will cause further changes in soil and
light conditions.
o The shading effect of the larger plants kills some of the smaller ones.
Stage 5
Eventually the area is colonised by dominant plant species and a climax community is reached.
o This would usually be oak woodland in the UK, but as we’re in Australia, a good example
would be a rainforest
Secondary Succession
Secondary succession is much the same as primary succession, except it occurs when the current
seral stage is removed abruptly.
o This may be due to a natural disaster such as a fire, or by human influence such as
deforestation and strip mining.
o This time, there is already soil and probably seeds present. This means the succession will
happen more rapidly than primary succession.
o The pioneer plants are windblown plants that are tolerant to high levels of sun and grow
fast. Fast growing trees then develop, while shade-tolerant species develop in the
understorey.
Primary vs Secondary Succession
Primary succession
Starts from bare rock or water.
Occurs in an environment that is devoid of vegetation, organisms and soil (such as a lava
flow or area left from retreated glacier).
Basically, it’s the gradual growth of an ecosystem over time.
Secondary Secession
Starts where there has been vegetation before.
, What is succession?
Is the process of gradual changes in an ecological community over a period of time. These changes
are orderly and generally predictable in the absence of major disturbances.
Primary Succession
Stage 1
Pioneer species are the first species to colonise an area, and tend to be lichen
o They are opportunistic species which are able to rapidly exploit a sudden new opening in
ground plant cover.
o They are able to withstand desiccation, extremes of temperature and low levels of nutrients.
o They must be able to grow quickly, but are usually short lived.
Stage 2
The pioneer species penetrate and break up the rock.
o As they die and decompose, humus builds up.
o This allows other simple plants such as mosses and ferns to now grow.
Stage 3
Mosses and ferns cast shade to stop further growth of lichens
o Their roots are longer and so further break up the rock.
o The organic matter gradually increases as these bigger plants die. More water is retained by
this, so grasses, small flowering plants and shrubs can grow.
Stage 4
Growth of larger plants and the animals which inhabit them will cause further changes in soil and
light conditions.
o The shading effect of the larger plants kills some of the smaller ones.
Stage 5
Eventually the area is colonised by dominant plant species and a climax community is reached.
o This would usually be oak woodland in the UK, but as we’re in Australia, a good example
would be a rainforest
Secondary Succession
Secondary succession is much the same as primary succession, except it occurs when the current
seral stage is removed abruptly.
o This may be due to a natural disaster such as a fire, or by human influence such as
deforestation and strip mining.
o This time, there is already soil and probably seeds present. This means the succession will
happen more rapidly than primary succession.
o The pioneer plants are windblown plants that are tolerant to high levels of sun and grow
fast. Fast growing trees then develop, while shade-tolerant species develop in the
understorey.
