Disturbance

Question 1

What is succession?

Answer 1

Gradual community change in an area following a disturbance

Question 2

What is a disturbance?

Answer 2

Any relatively discrete event that disrupts an ecosystem, community, or population structure and changes resources, substrate availability, or the environment

Question 3

What are examples of disturbances?

Answer 3

Forest fire
Windstorms
Pest outbreaks
Roadside construction

Question 4

What is a short-term disturbance?

Answer 4

Windstorms
Wind can destroy vegetation within only minutes to hours

Question 5

What is a long-term disturbance?

Answer 5

Glaciation
Glaciation can destroy vegetation and keep area devoid of life within thousands of years

Question 6

What is a local disturbance?

Answer 6

Off-road vehicle use

Question 7

What is a regional disturbance?

Answer 7

Drought

Question 8

What does disturbance lead to?

Answer 8

Succession
The type of succession that occurs depends n how extreme the disturbance was

Question 9

What is primary succession?

Answer 9

Gradual change in communities on newly exposed geological substrates

Question 10

What is secondary succession?

Answer 10

Gradual change in communities where the disturbance has destroyed a community without destroying the soil

Question 11

What are some characteristics of primary succession?

Answer 11

Existing vegetation is destroyed, new substrate created
No soil, no soil seed bank
Colonization via dispersal
Pioneer organisms are lichens, mosses, and vascular plants

Question 12

What are some characteristics of secondary succession?

Answer 12

Colonization by pioneer organisms but existence of soil gives succession a head start T
There is a seed bank, soil nutrients, and substrate for roots

Question 13

What are the stages of succession?

Answer 13

Disturbance
Annual plants
Grasses and perennials
Grasses, shrubs, pines, young oak and hickory
Mature oak and hickory forest

Question 14

What is a climax community?

Answer 14

A community that occurs late in succession and whose state remains stable until disrupted by a disturbance

Question 15

What is a disclimax community?

Answer 15

A community whose species composition is maintained through frequent disturbances

Question 16

What is the intermediate disturbance hypothesis?

Answer 16

The theory that intermediate levels of disturbance allow for the greatest species diversity

Question 17

What are levels of disturbance defined by?

Answer 17

Frequency of the disturbance
Severity of the disturbance

Question 18

What happens at high disturbance?

Answer 18

Lots of change
To little time for many species to colonize
Contain mostly organisms that are good colonizers
r-selected species

Question 19

What happens at low disturbance?

Answer 19

Little change
Competitive exclusion by species that are good competitors
K-selected species
Many are climax species

Question 20

What happens at intermediate disturbance?

Answer 20

A moderate amount of change
Sufficient time between disturbances for species to colonize, but not enough time to allow competitive exclusion
Community contains organisms that are good competitors and organisms that are good colonizers = higher diversity than at high or low disturbances

Question 21

What is the evidence supporting the intermediate disturbance hypothesis?

Answer 21

Intertidal pools

Question 22

How much evidence is there for the intermediate disturbance hypothesis?

Answer 22

Some ecologists have no found support when looking at different ecosystems because ecosystems are complex

Effect of the disturbance depends on the biology of the organisms in the system and the details of the disturbance

Question 23

Why would communities not change when disturbed?

Answer 23

Community stability

Question 24

What is stability?

Answer 24

The persistence of a community of ecosystem in the face of disturbance

Question 25

What is resistance?

Answer 25

The capacity of a community or ecosystem to maintain structure and/or function in the face of potential disturbance

Question 26

What is resilience?

Answer 26

The capacity to recover structure and/or function after disturbance
A highly resilient community or ecosystem may be completely disrupted by disturbance, but quickly return to its former state

Question 27

What are alternative stable states?

Answer 27

The existence of alternative communities that assembled after disturbance and deviate from the original or climax community

bottom of cup = stable state
movement of ball = disturbance

Question 28

What does increased diversity lead to?

Answer 28

Greater stability

Question 29

What is the insurance hypothesis?

Answer 29

Theory that increased diversity increases community stability due to an increased probability of there being some species present in the community able to cope with any particular disturbance