Download Section 2: Plant Succession

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
• The Monoclimax Concept
Pioneer Community
prisere
• 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).
Seral stages:
temporary
conditions which
develop over time
(plant succession)
Climatic climax
(natural vegetation)
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
e.g. deforestation
Temporary climatic
changes e.g. drought,
colder conditions
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 previous
management has been
discontinued e.g.
abandoned farmland due
to shifting cultivation in
the tropical rainforest
Primary Succession
Secondary Succession
Ecosystem Evolution
Bare surface
X
Deflected
Succession e.g.
severe disturbance
fire, hurricane
Primary
succession
Subclimax
Ecosystem
Deflected
Succession e.g.
relief restricts
development
Partial displacement e.g.
grazing
Climatic Climax
Ecosystem
Plagio Climax
Ecosystem
Relic
Ecosystem
Sudden displacement e.g.
logging
Secondary succession e.g.
natural regrowth
Secondary succession e.g.
development of a
farmed ecosystem
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