Communities change over time through succession, which involves a changing sequence of species colonizing new or disturbed land. Primary succession starts with new land being colonized first by lichens and mosses, then shrubs and small trees, and eventually a climax community of mature hardwood forests. Secondary succession starts with already formed land and is usually triggered by disturbances like fires or storms, where species colonize the disturbed material.

2. Communities Change
Time
Ove
r
Succession: a process of
community development that
involves a changing sequence
of species

3. • Starts with new land.
• Species land on new material
and colonize (pioneer
community).
• Starts with lichens, moss, and
Primary Succession

4. 1) Lichens: Can be N fixers  Put
Nitrate into soil for other plants to
grow!

5. 2) Small Shrubs and mosses (little roots),
provide habitat

6. 3) Young pine trees more habitat

7. 4) Mature hardwood and deciduous
forests climax community

8. Secondary Succession
• Starts with already formed land.
• Species land on disturbed material.
• Disturbance usually caused by fires, storms,
and man.

10. Fire Succession in Chaparral
• Needed for:
– Reproduction
– Clearing out
competitors
– Germination
(seed
sprouting)

11. As Ecosystems Mature
• Increase in:
1. Diversity & pop
numbers
2. System
stability
3. Biomass
4. Nutrient Hold
Capacity