Community Theory

Question 1

What are the stages of succession?

Answer 1

Disturbance

Primary succession

Secondary succession

Question 2

What is primary succession?

Answer 2

land with no soil (e.g., newly exposed land or new oceanic islands).
takes thousands of years to recover

Question 3

What is secondary succession?

Answer 3

areas with existing soil (e.g., after a forest fire or agricultural abandonment).
takes hundreds of years to recover

Question 4

Name six different drivers that can cause disturbance in plant communities.

Answer 4

Fire

Wind

Water (floods, erosion)

Drought & parasite outbreaks

Deforestation & mining

Overgrazing

Question 5

What are the traits almost always required in pioneer plants?

Answer 5

Nitrogen fixation
Help improve soil quality
Adapted to extreme conditions

Question 6

What is the Facilitation Model of succession?

Answer 6

Early species improve conditions for later species.
Example: Lichens and mosses help create soil for larger plants in primary succession.

Question 7

What is the Inhibition Model of succession?

Answer 7

Early species hinder later arrivals through competition.
Example: Invasive grasses like Bromus tectorum outcompete native species

Question 8

What is the Tolerance Model of succession?

Answer 8

Succession is shaped by species’ ability to survive the current conditions, with no strict order.
Example: Old-field succession, where species arrive based on dispersal ability and tolerance.

Question 9

How is a gap dynamics model different from a climax state forest model?

Answer 9

Gap dynamics: Small disturbances (e.g., treefalls) allow succession to return to the pre-disturbance state, maintaining community diversity.

Climax state model: Suggests a stable, final community exists until a large disturbance occurs, representing the endpoint of succession.

Question 10

What is the intermediate disturbance hypothesis?

Answer 10

Intermediate levels of disturbance maximize species richness.

Question 11

Which major Earth biome would not exist with frequent disturbance by fire?

Answer 11

Grasslands and savannas

Question 12

Briefly explain Clement’s perspective on communities.

Answer 12

Clement believed succession followed a predictable path toward a climax community determined by climate.
Example: A temperate forest reaching a stable state after succession in a specific climate zone

Question 13

Briefly explain Gleason’s perspective on communities

Answer 13

Gleason believed no two communities are exactly alike, and species persist by chance.
Example: A wildflower meadow with varying species composition due to random dispersal and environmental conditions.