Communities - Succession

Question 1

What are the processes and mechanisms of succession?

Answer 1

Succession progresses in seral stages beginning with vegetation and moving into the return of animals

Question 2

What are the differences between primary and secondary succession?

Answer 2

Primary: starting again from nothing - no existing biota, seed bank, or top layer

Secondary: large setback but not completely starting over - some biota retained, seed bank is present, top layer is present

Question 3

What are some disturbance processes that may lead to succession?

Answer 3

Fire, deglaciation, earthquakes, flooding…

Question 4

Link concepts from evolution, physical environment,
populations, etc. to describe succession

Answer 4

The physical environment may be disturbed by chance abiotic events, the species that can adapt will pass on their beneficial traits to their offspring. These individuals will make up the new population of a climax community.

Question 5

Disturbance

Answer 5

An event that causes damage or destruction to some part of a community or larger landscape

Question 6

Succession

Answer 6

Process of community-level recovery after disturbance

Question 7

Resiliance

Answer 7

Ability to recover original condition after a distrubance

Question 8

Resistance

Answer 8

Ability to avoid displacement from a disturbance

Question 9

Characteristics of disturbance

Answer 9

Frequency, intensity, scale, return frequency

Question 10

Disturbance frequency

Answer 10

Regularity of the disturbance event

Question 11

Disturbance intensity

Answer 11

Severity of the disturbance event

Question 12

Disturbance scale

Answer 12

Microdisturbance: local-scale (ex. tree falls down)
Large scale stand-replacing: entire community is affected, leads to shifting mosaic succession (patches of varying successional stages)

Question 13

Return frequency

Answer 13

Regular: cyclical and predictable (ex. seasonal)
Irregular: stochastic and unpredictable

Question 14

Seral stage

Answer 14

One of several transitional community types (sere) during succession

Question 15

Climax community

Answer 15

Stable, predictable endpoint to succession, but still dynamic

Question 16

Characteristics of early succession

Answer 16

Ruderal and survivor species - fast growing, tolerant of high temperatures and light, good dispersers

Question 17

Characteristics of mid succession

Answer 17

Pioneer trees and shrubs - stress tolerant, shade adapted

Question 18

Characteristics of late succession

Answer 18

Competitive trees and shrubs - slower growing, less disturbance tolerant, dominant community

Question 19

Aquatic succession

Answer 19

Stages are called hydroseres - edges of lake fill with sediment, vegetation grows, and eventually the lake is filled in

Question 20

Alternative stable states

Answer 20

Ecosystems are dynamic and may have several possible stable states. The current state is determined by interactions between species, the species available, and abiotic changes

Question 21

Facilitation model

Answer 21

Early seral stages help the establishment of later stages by “prepping” the environment

Question 22

Tolerance model

Answer 22

Species occupy different niches, so they can only exist in certain seral stages where there niches are realized

Question 23

Inhibition model

Answer 23

Early species inhibit the establishment of later species. Later species only establish themselves as a result of further disturbance

Question 24

How does vegetation spread (5)?

Answer 24

Vegetative (budding)
Advanced regeneration (young only released when old die)
Long distance dispersal of seed
Serotiny (retention of seed in woody capsules - released by fire)
Seed bank (seed accumulation in the soil)

Question 25

Succession impacts on life history… early vs. late

Answer 25

Early succession species: short-lived, fast growth, many small seeds

Late succession species: taller, shade canopy, deep roots, longer lived, slow growth, fewer larger seeds

Question 26

How does disturbance change the structure and function of a community?

Answer 26

Depends on frequency and intensity - often damages soil quality, destroys vertical profile, and decreases biodiversity

Question 27

Transient climax

Answer 27

Frequent disturbance exceeds resistance & resilience - locked in a particular seral stage

Question 28

Fire/grazing-maintained climax

Answer 28

Fire/grazing prevents the following seral stages - new climax established

Question 29

Primary succession

Answer 29

All existing biota are removed, no seed bank, no top layer of soil

Unpredictable climax community, colonized by long-distance dispersal

Ex: deglaciation

Question 30

Secondary succession

Answer 30

Some biota is retained, seed bank exists, top layer of soil remains

More predictable climax community, shifting mosaic

Ex. clearcut