Section 2: Plant Succession

Plant communities develop through a succession of changes.

Key Ideas: - Seral Stages- Climatic Climax Vegetation- Plagioclimax Vegetation

Case study : Psammoseres (sand dunes) e.g. Murlough Nature Reserve outside Newcastle

Biogeography: The study of the distribution of plants and animals over

the earth’s surface.• ‘Nature abhors a vacuum’• i.e. if plants die something will always replace

them. When new land is created, e.g. a lava flow, new species will move into that area and take over.

• Algae & lichen will colonize rock and break it down (weather it) to form soil.

• The formation of soil then allows other plants to take over.

What is vegetation succession?

• PRISERE is the term for vegetation succession. It is the complete chain of successive seres beginning with a pioneer community and ending with a climax vegetation.

• Vegetation succession occurs because the environmental conditions change. This happens gradually for lots of plants to develop.

• Each stage is called a SERAL STAGE.• Each stage sees the development of species

which cause the micro environment to change which in turn lets new species move in and become dominant.

The MONOCLIMAX CONCEPT• F.E. Clements (1916) said that

for each climatic zone only one type of climax vegetation could evolve.

• He called this the climatic climax vegetation. It is now more commonly known as the monoclimax concept.

• This occurs when the vegetation is in harmony with the local environment.

• As seral stages develop the number of species and height of the plants increase.

• Each sere tends to be named after the dominant species ( the largest or most numerous species).

• The Monoclimax Concept

Pioneer Community

Climatic climax(natural vegetation)

pris

ere Seral stages:

temporary conditions which develop over time(plant succession)

What is Britain’s Biome? P.306

Britain’s Climate

• Cool temperate due to our island position• Cool summers (winds off Atlantic cooling

influence– water slower to heat up than land)• Mild winters (winds off Atlantic warming

influence – water holds its heat for longer & warm ocean current North Atlantic Drift)

• Rain in all seasons

• HOW DOES THIS INFLUENCE VEGETATION?

Britain’s Vegetation

• Our natural Climatic Climax Vegetation is broad leaved deciduous forest.

• The dominant vegetation is influenced by soil type, rock type and climate if people do not interfere.

• So why is Britain not covered in woodland?• Human activities have cut down many trees (farming &

urban growth).• Trees do not exist on mountains – relief, soils & climatic

factors.• Coniferous trees (fast growing) are planted which are not

native.

Britain’s Vegetation:

• The vegetation cover in much of Britain is a PLAGIOCLIMAX VEGETATION.

• This is a deflected climax vegetation that occurs when people have damaged the natural climatic climax so much that regeneration is not possible.

• In the UK you now have grassland instead of woodland.

Possible interruptions:Natural interruptions Human interruptions

Tectonic activity e.g. volcanic eruptions

Temporary climatic changes e.g. drought,

colder conditions

e.g. deforestation

Plagioclimax Vegetation(if permanent)

The Polyclimax Theory• The monoclimax concept has been

replaced by the polyclimax theory.• This theory acknowledges the importance

not only of climate, but of several (poly) local factors including :- drainage- parent rock- relief- microclimate- human activity

The polyclimax theory (p.287)

New or previously sterile land surface,

or in water

Land on which previousmanagement has been

discontinued e.g. abandoned farmland dueto shifting cultivation inthe tropical rainforest

Primary Succession

Secondary Succession

Ecosystem EvolutionBare surface

SubclimaxEcosystem

RelicEcosystemX

Climatic ClimaxEcosystem

Plagio ClimaxEcosystem

DeflectedSuccession e.g.

relief restrictsdevelopment

DeflectedSuccession e.g.

severe disturbance fire, hurricane

Prim

ary

succ

ess

ion

Sudden displacement e.g.logging

Secondary succession e.g.natural regrowth

Secondary succession e.g.development of a farmed ecosystem

Partial displacement e.g.grazing

Primary Successions (p.284)

Transect across sand dunes to show a PSAMMOSERE.

Primary succession on a psammosere.

Colonisation of fore-dunes.

Transect showing a primary succession in a HALOSERE(river estuaries where silt deposited by the

ebbing tides and inflowing rivers)

Primary succession in a halosere.

Primary succession in a HYDROSERE(lakes and ponds – sediment carried into the lake

will enrich the water and begin to infill it)

Primary succession in a hydrosere

Field sketch of a LITHOSERE on a newly emerging rocky coastline (raised beach), Arran.

Primary succession in a LITHOSERE

Lichens, mosses and grasses on a rocky coastline