Succession is the gradual change over time in the species that form a community. Primary succession occurs in areas with no soil or plants, beginning with pioneer species like lichens that help form soil. Over time, mosses, herbs, and larger plants establish, building more complex communities as soil and nutrients accumulate. Secondary succession follows disturbances that remove existing species, allowing survivors and new colonizers to repopulate the area through similar successional stages.

1. Succession

2. Succession
Succession – gradual change over time in the species that
form a community

3. Succession
Primary succession – succession in an area that has no
plants, animals, or soil

4. Succession
Pioneer species – first species to colonize an area during
succession (usually lichens).
Lichens secrete acids that erode rock to form soil.

5. Succession
Over time, mosses and other small plants colonize. They
keep water in the soil to reduce erosion.
Lichens decline because they require bare rock, which is
now covered with soil.

6. Succession
The vegetation attracts insects, birds, and other small
animals.
Plant and animal decomposition builds soil.

7. Succession
Small herbaceous plants eventually outcompete mosses.
Roots continue to break the rock below which adds
nutrients to the soil.

8. Succession
Eventually large herbaceous plant appear.
Some small plant populations decline because they are
outcompeted for sunlight, water, and nutrients.

9. Succession
Secondary succession – succession in an ecosystem that
has been disturbed by a natural event or human activity

10. Succession
When the disturbance occurs, several plants and animals
die.
Usually a few plants or animals survive. They will begin to
repopulate the area.

11. Succession
Human activity and succession:
Many human activities get in
the way of succession.
i.e. - growing monocultures
of grass
-destroying non-grass
species/using herbicides
- paving soil with
cement/concrete