Succession and climatic climax

Question 1

What does the composition of vegetation rely upon?

Answer 1

Natural factors:
Climate, relief and soils.
Human factors:
Clearance, fires and livestock grazing.

Question 2

What is a plant succession?

Answer 2

Plants become more complex over time.

‘The change in a plant community through time’.

Question 3

When is a climatic climax achieved?

Answer 3

Undisturbed succession - climatic climax.

Plant species live in a perfect balance with the current environmental conditions.

Question 4

What factors affect plant growth? 4

Answer 4

Climate.
Drainage.
Geology.
Relief ect.

Question 5

What is a primary succession?

Answer 5

Occurs on surfaces that have had no previous vegetation.
Includes lava flows, bare rock and sand dunes.
Main types: Xreoseres and Hydroseres.

Question 6

Where is a Xerosere formed?

Answer 6

Formed on dry land.
Lithoseres - rock.
Psammoseres - sand dunes.

Question 7

Where is a Hydrosere formed?

Answer 7

Formed in water.
Haloseres - salt water.
Hydroseres - fresh water.

Question 8

What is a secondary succession/when does it occur?

Answer 8

After the destruction/modification of an existing plant community.
Can occur naturally e.g. fire caused by lightening/deforestation.

Question 9

What is a sere?

Answer 9

An individual stage in a plant succession.

Invasion, colonisation, competition, domination and decline.

Question 10

What is the first general stage of plant succession? 7 points.

Answer 10

Pioneer species - can survive harsh conditions.
Invade bare ground (dispersal/migration) = colonies of 2+ species established.
E.g. long-rooted salt-tolerant marram grass in a sand dune.
Compete for space/light/water/nutrients.
Dying - adds organic matter to soil.
Can affect microclimate and soil conditions.
Roots break up/weather the surface - aids soil formation.

Question 11

What is the second general stage of plant succession? 7 points.

Answer 11

Improved ground by immature soil.
Other plants colonise.
Each stage has improved conditions - more species.
Organic matter improves structure/water-rendition.
Allows taller plants - more in demand of water/nutrients.
Provide shelter from wind/sun - other plants colonise.
Dominant plants - tallest.

Question 12

What is the third general stage of plant succession?

Answer 12

Thousands of years - stability.
Dominants rule over rivals.
Species decrease.
Community becomes 'closed' - saturation point has been reached with all potential niches occupied.
CLIMATIC CLIMAX COMMUNITY.

Question 13

What is polyclimax theory?

Answer 13

Local factors e.g. drainage/geology, can create variations in a climatic climax community.

Question 14

What is an example of a lithosere?

Answer 14

Begins life on newly exposed rock surface.
E.g. eruption of a volcano leaves a new, bare lava surface - Surtsey 1963, Iceland.
Raised beaches e.g. west coast Scotland.

Question 15

What is the FIRST STAGE of succession of a lithosere?

Answer 15

FIRST STAGE:
The bare rock surface - very dry - rapid runoff.
Only bacteria/algae present.

Question 16

What is the SECOND STAGE of succession of a lithosere?

Answer 16

SECOND STAGE: lichens - withstands the water shortage. Break down the rock/reduce water levels.
E.g. Rinodina lichens.
Wind borne soil particles/organic matter collect in the depressions - soil formation.
Helps growth of foliose lichens e.g. Parmelia.
Retain more water/accumulate more soil particles - develops fine layer of soil on the rock surface.

Question 17

What is the THIRD STAGE of succession of a lithosere?

Answer 17

THIRD STAGE:
Soil/humus accumulation - moss growth - e.g. Grimmia.
More soil/organic matter accumulation - favour moisture loving mosses e.g. Hypnum (more advanced).

Question 18

What is the FOURTH STAGE of succession of a lithosere?

Answer 18

FOURTH STAGE:
Decaying mosses - herb layer.
Helps germination to seeds of hardy grasses e.g. Poa.
Decomposition of annual grasses - replacement by perennial grasses e.g. Heteropogon (lives for 2+ years).
Small animals invade.

Question 19

What is the FIFTH STAGE of succession of a lithosere?

Answer 19

FIFTH STAGE:
Further weathering/herb deaths - shrub growth - e.g. Rhus.
Larger size/deeper roots - more weathering/soil formation.

Question 20

What are the FIFTH/SIXTH STAGES of succession of a lithosere?

Answer 20

SIXTH STAGE: fast-growing pioneer trees e.g. willow.

SEVENTH STAGE: slower-growing trees e.g. ash.
Appear in later stages - initially in shrub shade.
Temperate deciduous woodland dominants.