Ecology - Lecture 13 - Succession

Front 1

Define:

Community

Back 1

Any assemblage of living organisms in a prescribed area or habitat.

Can be of any size, and any taxonomic composition.

Front 2

What are the 2 opposing views of what a community constitutes?

What "big question" does this ask?

Back 2

1) Community as a "super-organism". (similar to the "web of life")

2) "Individualistic" view


Big Question:
"Is the community an organized system of recurrent species OR a haphazard collection of a population with minimal integration?"

Front 3

Define:

Succession

Back 3

The directional change in community composition over time.

Front 4

What are the 2 main types of succession?

Describe them briefly.

Back 4

1) Primary Succession - Colonization of a new, *sterile* site.

2) Secondary Succession - Recolonization of a disturbed site.

Front 5

The colonizing of an area near a volcano after a massive eruption would be an example of which type of succession?

Back 5

Primary Succession

*The volcano's lava would sterilize (kills all life) an area around the volcano, thus making this an example of primary succession.

Front 6

The colonization of a forest after a large forest fire would be an example of what type of succession?

Back 6

Secondary Succession

*There would still be bacteria living in the soil underneath the burned layer (i.e. the site is not completely sterile), thus making this an example of secondary succession

Front 7

What are 3 characteristics of a geographic site that would allow for Primary Succession?

Back 7

1) Sterile habitat (i.e. no plants, seeds, or bacteria in the soil)

2) Low or no nutrient availability.

3) Erosion

Front 8

What are 3 characteristics of a geographic site that would allow for Secondary Succession?

Back 8

1) Disturbance can be of any size.

2) Seed bank of later successional species present (i.e. the site is *not* sterile)

3) Bacteria and other soil organisms present.

Front 9

Define:

Old Fields

Back 9

Land that was formerly cultivated/grazed (i.e. used for agriculture) but later abandoned.

Front 10

Define:

Obligate Seeder

Back 10

Plants with large, fire-activated seed banks that germinate, grow, and mature rapidly following a fire in order to reproduce and renew the seed bank before the next fire.

*source: Wiki

Front 11

Chaparral shrubs after fire:

Adenostoma (Chamise) is an example of a _____.

Back 11

resprouter/seeder

Front 12

Chaparral shrubs after fire:

Ceanothus is an example of a _____.

Back 12

Obligate seeder

Front 13

Describe the policy of fire suppression over the 1900's.

What is policy theorized to have caused?

Back 13

- Policy of fire suppression started in the early 1900's.

- Caused changes in the forest structure.

- Increased the density of trees.

- Shift from fire tolerant, shade intolerant TO fire sensitive, shade-tolerant species.
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Theorized to have increased the magnitude of fires that occur.

- Higher densities increased the fuel load.

- Understory of trees provided "ladder fuel"

- Overall increased risk of catastrophic, stand-replacing crown fire.

Front 14

What are the 4 main Models of Succession used?

Back 14

1) Facilitation Model

2) Inhibition Model

3) Tolerance Model

4) Random Colonization Model

Front 15

Models of Succession:

Describe the Facilitation Model
(4 pts)

Back 15

1) Habitat colonized by a "pioneer species"
- Usually weeds (good dispersal power, rapid growth)

2) Pioneer species modify the environment (i.e. changes the soil structure and nutrient availability)

3) This modification facilitates colonization by other species

4) A climax community is reached (i.e. a stable endpoint)

Front 16

Models of Succession:

Describe the Inhibition Model
(4 pts)

Back 16

1) "Who gets there first" is important

2) Initial species inhibits others from colonizing

3) Sequence is less predictable

4) A climax community is reached.

Front 17

Models of Succession:

Describe the Tolerance Model
(3 pts)

Back 17

1) Any species can start succession

2) Good competitors predominate in climax community

3) Initial community composition directs succession.

Front 18

Models of Succession:

Describe the Random Colonization Model
(3 pts)

Back 18

1) The "Null model"

2) No facilitation or inhibition

3) Succession is caused by:
- Change survival of different species
- Random colonization by new species

Front 19

Define:

Climax Community

Back 19

The final or stable community in a successional series.

- Self-perpetuating
- In equilibrium with physical and biotic environment

Front 20

Who came up with the Monoclimax Hypothesis?

What does this hypothesis say?

Back 20

F.E. Clements in 1936.

- One region, one climax community

- Climax community produced entirely by region's climate.

Front 21

Who came up with the Climax-Pattern Hypothesis?

What does this hypothesis say?

Back 21

R.H. Whitaker in 1953.

- Climax at any location is a result of all environmental factors such as:
{climate, soil type, fire, biotic factors, wind}

- Climax community for a contiuum along environmental gradients

Front 22

Of the following hypotheses:

- Monoclimax Hypothesis
- Climax-Pattern Hypothesis

...which is generally accepted by ecologists today?

Back 22

Climax-Pattern Hypothesis