This presentation summarizes the key concepts of an ecological succession, citing clear examples. It gives readers an understanding of the stages involved in both primary and secondary succession.

1. Ecological Succession
Amos Watentena
wateamos@gmail.com

2. Succession is a gradual process
• Newer communities make
it harder for the older
ones to survive.
• Example: Younger birch
trees will have a harder
time competing with
taller, older birch trees
for sun, but a shade loving
tree may replace the
smaller birch trees.

3. Ecological Succession
A natural process of change and
replacement of the types of species in a
community.
It takes hundreds or thousands of
years to occur.
And it is divided into two distinct
stages i.e. primary and secondary.

4. Primary Succession
Type of succession that
occurs where there was
no ecosystem before.
Occurs on rocks, cliffs,
and sand dunes.
Primary succession is
very slow.
Begins where there is no
soil.

5. Lichens start to grow
Takes several hundred years to produce fertile
soil naturally.
First species to colonize bare rock would be
bacteria and lichens.
Do not require soil.
Colorful, flaky patches.
Composed of two species, a fungi and an algae.
The algae photosynthesize and the fungi
absorbs nutrients from rocks and holds water.
Over time, they break down the rock.

6. Lichens starts to die
As the rocks breaks
apart, water freezes
and thaws on the
cracks, which breaks
up the rocks
further.
When the lichens
die, they accumulate
in the cracks.

7. Mosses starts to grow
Then mosses begin to
grow and die, leading to
the creation of fertile
soil.
Fertile soil is made up of
the broken rocks,
decayed organisms,
water, and air.
Primary succession can
be seen happening on the
sidewalks.

8. Secondary Succession
It is the most common form of
succession
Occurs on a surface where an
ecosystem has previously existed.
Occurs on ecosystems that have been
disturbed or disrupted by humans,
animals, or by natural processes such as
storms, floods, earthquakes, and
volcanoes.

9. An example of Mt. St. Helens
Erupted in 1980.
44,460 acres were
burned and flattened.
After the eruption,
plants began to colonize
the volcanic debris.
Pioneer species: the
first organism to
colonize any newly
available area and begin
the process of
ecological succession.

10. Climax Community
Climax community:
the final and stable
community.
Climax community
will continue to
change in small
ways, but left
undisturbed, it will
remain the same
through time.
Over time, the pioneer
species makes the area
habitable by other species.
Today, Mt. St. Helens in the
process of secondary
succession.
Plants, flowers, new trees
and shrubs have started to
grow.
If this continues, over time
they will form a climax
community.

11. Fire and Secondary Succession
Natural fire caused by lightening are a
necessary part of secondary succession.
Some species of trees (ex: Jack pine)
can only release their seeds after they
have been exposed to the intense heat
of a fire.
Minor forest fires remove brush and
deadwood.

12. Some animals
depend on fires
because they feed
on the newly
sprouted vegetation.
Foresters allow
natural fires to burn
unless they are a
threat to human life
or property.

13. Secondary Succession
Occurs in farmland
that has been
abandoned.
Grasses and weeds
grow quickly, and
produce many seeds
that cover large areas.

14. Over time, taller plants grow in the
area, shading the light and keeping the
pioneer species from receiving any light.
The longer roots of the taller plants
deprive the pioneer species from water.
The pioneer species die.

15. Taller trees begin to grow
and deprive the taller
plants of water and light.
Followed by slow growing
trees (oaks, maples)
takeover the area.
After about a century, the
land returns to a climax
community.

16. Thank you