module 14

Question 1

Communities are in

Answer 1

constant flux

Question 2

communities appear

and what changes

Answer 2

Appear stable in short-term
Change over Long-Term
Environmental Conditions
Competition 
Facilitation

Question 3

community development is

Answer 3

chaotic, cyclical, or directional (succession)

Question 4

Succession

Answer 4

Gradual, Ordered, Directional change in plant and animal communities in an area following a disturbance or the creation of new substrate

Question 5

Basic Succession – F.E. Clements

Answer 5

follows orderly series of species replacement

does not guarantee outcome (single climax)

Question 6

Primary Succession

Answer 6

Sequence of communities developing in newly exposed habitat devoid of life

Succession only from Immigrants

Question 7

Secondary Succession

Answer 7

Sequence of communities developing in habitats in which the climax has been disturbed or removed

Succession from Immigration or Seed Bank

Question 8

Autogenic Succession
organisms change environment to
time scale

Answer 8

Temporal succession of species at a location driven by processes operating within community

• Organisms Change Environment to harm/favor others
• Time Scale – Life of Organisms
• biotic factors

Question 9

Allogenic Succession

Answer 9

Temporal succession of species at a location driven by external influences which alter conditions

• Massive Disturbances, Environmental Shifts
• Time Scale – Time scale of disturbance

Question 10

Sere

Answer 10

A series of stages of community development in a particular area leading to a stable state, or Climax

Question 11

final Seral Stage

may be….

Answer 11

• Climax
• -Final Seral Stage
• -Endpoint of a successional sequence
• -A Community that has reached a steady state under a particular set of environmental conditions
• May be definitive or Tenuous

Question 12

Seres are different for and are determined by

Answer 12

-Different for each environment
-Determined by surrounding:
Vegetation
Nutrients
Soil Characteristics
Etc.

Question 13

Sand Dunes

Answer 13

• Soils Unstable/Shifting
• Low Nutrient Content
• 1st colonizers:
• -Stabilize soil
• -Add Organic material

Question 14

old fields

Answer 14

Old Fields

• -Soils More Stable
• -Higher Nutrients
• quicker to colonize

Question 15

closed community

Answer 15

Closed Community

• Clementsian View
• Species closely associated
• Ecological limits of Individual Species = Ecological Limits of Community
• Ecotones Distinct
• -Transition between communities well defined

Question 16

open community

Answer 16

• Gleasonian View
• Species distributed independently
• No Natural Boundaries

Question 17

Climax – Early Studies

Answer 17

Determined solely by
climate
-Similar Climaxes within the Same Regions

Question 18

Clementsian Climax

-how many climaxes

Answer 18

Identified 14 climaxes in North America
-2 grasslands, 3 scrub, and 9 forest
All others were interrupted seral stages
-Fire, animals, soils, topography
Sub-climaxes could persist unchanged for long periods
-Due to “unnatural” disruptions to seral stages

Question 19

Present Day Climax

Answer 19

Early Ideals Questioned or Dismissed for Open Community Concept
-local climaxes

Communities Vary Continuously over Gradients

Question 20

Continuum Index

Answer 20

change in community composition based on environmental gradient

Question 21

Succession begins with

Answer 21

disturbance or creation of new habitat

-Opens areas for Colonization of New Species

Question 22

succession driven by

Answer 22

Driven By Plants Differential Ability to:

• colonize
• compete

Question 23

Disturbances definitions

Answer 23

• Any Process that limits plants by destroying plant biomass (Grimes 1977)
• Any discrete, punctuated, killing, displacement, or damaging of ≥ 1 individuals that creates opportunity for new individuals (Sousa 1984)
• Any relatively discrete event that disrupts structure & changes resources, substrate availability, or physical environment (White & Pickett 1985)

Question 24

types of disturbances

Answer 24

• Physical Disturbance

- Biological Disturbance

Question 25

succession disturbances

Answer 25

Set Back Succession Remove all Life from area Eruption of Mt. St. Helens

Question 26

Old Field Succession

Answer 26

Changes Fast Initially Slows over time Slow Growing Plants

Question 27

Colonization occurs from:

Answer 27

areas surrounding disturbed area areas some distance away from disturbed area seed bank Disturbance may leave individuals remaining alive

Question 28

Colonization Primary Force in Succession | -Succession directed by Species’ Ability to:

Answer 28

Cope with Environmental Conditions Often Low Nutrients Disperse into Disturbed Areas Modify Environment

Question 29

Pioneer species | have the best combination of what

Answer 29

Species that are among the first to become established Best combination of Coping & Dispersal Often Determine Successive Colonizers

Question 30

best colonizers are | slower colonizers are

Answer 30

Best Colonizers often worst Competitors - Weeds - -Invade Quickly But are short lived - -Generally do not persist past 1 year ``` Slower Colonizers (grasses) Do persist -Thrive After death of weeds ```

Question 31

Major determinants of organisms in seral stage

Answer 31

Life History of Organisms Are Organisms Built for dispersal or competition? Evolutionary History of Species Nature of Changes

Question 32

Mechanisms of Succession

Answer 32

Pioneer Species Effect Future Colonizers Clements – 1 Mechanism ``` Connell & Slayter (1977) Presence of one species effects the probability of establishment of a second in 3 ways: Facilitation Inhibition Tolerance ```

Question 33

Facilitation

Answer 33

Many species may attempt to colonize newly available space. -Only certain species will establish. Pioneer Species modify environment so it becomes: -Less suitable for themselves -More suitable for species of later successional stages. Autogenic processes inherent in driving process -Addition of Organic Material -Breakdown of Substrate to Soil Key process in Primary Succession

Question 34

Tolerance

Answer 34

Initial occupants neither increase nor decrease the ability of other species to colonize -Initial stages of colonization are not limited to pioneer species. --Generally Better Nutrients & Soil remain Change driven primarily by Allogenic Processes -Early successional species do not facilitate later successional species.

Question 35

Inhibition

Answer 35

Early occupants modify the environment in ways that makes it less suitable for both early and late successional species. - Early arrivals inhibit colonization by later arrivals. - Assures late successional species dominate an area - They live a long time & resist damage by physical and biological factors. Succession driven Primarily by Allogenic Processes -Autogenic Processes present but impede change

Question 36

Founder Effect

Answer 36

- Two Supremely Competitive Species Colonize area - Propogules of neither species competes with adults of other - The species that establishes first determines community structure & direction of succession

Question 37

animal species _____ with plants

Answer 37

-Continuation of Succession --Woody Species Increase 1st small shrubs -> Small Trees ->Large Trees -Animal Species Increase with Plants

Question 38

Primary Succession in Glacier Bay

Answer 38

4 Stages - Pioneer Stage – blue-green algal mats, lichens, liverworts, forbs, limited willows, cottonwoods, spruce, & Dryas - Dryas stage – Thick mat of Dryas, few willows, alders, spruce. ~ 30 years after Retreat - Alder Stage – Alder dominated, ~ 50 YAR - Spruce Climax – ~ 100 YAR

Question 39

Ecosystem Changes During Succession | -soil depth and organic content

Answer 39

- Substantial changes in ecosystem structure during succession at Glacier Bay. - Total soil depth and depth of all major soil horizons show significant increase from pioneer community. - organic content, moisture, and N concentrations all increased. - Physical and biological systems are inseparable.

Question 40

Climax & Environment | rate of change and rate of adaptation

Answer 40

-Climax occurs when Community & Physical Environment reach Equilibrium Rate of Change of Environment < Rate of adaptation of Existing Organisms - Climax Remains Until Disturbance Occurs - Subtle Changes Continue even at Climax - -Births, Deaths, & Growth Processes - -Less Dramatic than succession