Biotic change, Lecture 35

Question 1

Are all communities dynamic?

Answer 1

yes, there biomass and composition changes through time

Question 2

Two types of factors that promote comumuninty change

Answer 2

extrinsic and intrinsic

Question 3

Extrinsic factors promoting community change

4

Answer 3

climatic
geomorphological
edaphic
anthropogenic

Question 4

Edaphic meaning

Answer 4

produced or influenced by soil

Question 5

Intrinsic factors promoting community change

6

Answer 5

invasion
competition
predation
parasitism
disease
speciation (evolutionary change)

Question 6

Three types of change in communities

Answer 6

1. regeneration
2. fluctuational
3. sucessional

Question 7

Types of change:

Regeneration

Answer 7

Results from natural processes of germination, growth and death of component individuals without a change in the amount or composition of vegetation

Question 8

Types of change:

Fluctuational (or reversible)

Answer 8

when biomass or composition varies from a mean state over shorter or longer periods of time

Question 9

Types of change:

Successional (directional or non- reversible)

Answer 9

Involves a change from one type of biomass or community to another in time

Question 10

Is regeneration a continous process?

Answer 10

yes,

maintain composition and structure of vegetation

Question 11

Main consequence of regeneration?

Answer 11

uneven age distribution of individuals

Question 12

Cyclic gap regeneration

Answer 12

a major process in regenerative vegetation change, creates mosaics in many different communities

Question 13

What does fluctuational change result from?

Answer 13

1. phenological changes aossicated with seasonal climatic regimes (warm/cold, wet/dry) (seasonal changes in total biomass)
2. short-term environmental variation

Question 14

Short-term environmental variation resulting in fluctuational change
2

Answer 14

1. effects depend on intensity and duration of deviation from mean conditions
2. climatic deviations for a few years is common and
   can change relative importance of component species in community

Question 15

Successional change

Answer 15

A sequential change in form and compositio of biomass through time

Question 16

Once started, succession is biotically controlled:

2

Answer 16

1. progressive habitat modification

2. later interspecific competition

Question 17

Climax stage is dominated by

Answer 17

the largest and tallest plants, capable of maintaing themselves in the prevailing climatic conditions

Question 18

Sub-climaxes

Answer 18

• local physical conditions slow succession

- eventually reaches climatic climax

Question 19

Plagioclimax

Answer 19

extreme human activities can deflect succession from natural course

Question 20

Plagioclimax vegetation

2

Answer 20

chalk grasslands, lowland heathlands

Question 21

Clement’s theory

Answer 21

Irrespective of the initial substrate, succession results in same vegetation communities for a given a climate: climatic climax

Question 22

Disadvantages of clement’s model

Answer 22

too simplistics and there may be a range of types of succession for a particular habitat

Question 23

Processes involved in succesion

4

Answer 23

1. facilitation
2. tolerance
3. inhibition
4. random

Question 24

Facilitation

processes involved in succesion

Answer 24

Early estalished species modifty habitat mkaing it more suitable for the later colonists

Question 25

Tolerance (competition)

processes involved in succesion

Answer 25

Faster-growing but less tolerant species establish,
Slower-growing, more tolerant (competitively superior) species invade and mature,
Early colonists eventually excluded

Question 26

Inhibition

processes involved in succesion

Answer 26

first plant species to become established inhibit further invasion until they eventually die

Question 27

Random

processes involved in succesion

Answer 27

Chance survival of different species when succession is initiated,
subsequent random invasion by new species - all grow and mature at different rates