Succession Flashcards
What is succession
The process of change in the structure and composition of a biological community over time
What two types of factors govern a species’ distribution?
Biotic
Abiotic factors
What changes do communities undergo over time?
Changes in: Composition Structure Diversity Productivity
What 4 ways can communities change over time
- Dispersal of species to new habitat
- New species replacing existing species
- New growth becoming old growth
- Disturbance events such as fire/ natural disasters
Define primary succession
the colonisation of habitats devoid of life
Where/ when does primary succession begin?
When an area is completely lifeless and soil has not yet formed i.e: barren rock/ rubble
What organisms colonise an area first in primary succession (2)
Prokaryotes and heterotopic bacteria
Which organism succeeds bacteria in primary succession?
Lichens and mosses
Describe the brief process of primary succession
Bacteria - Lichens and moss - grasses and shrubs - trees (Followed by animals etc)
What does soil form from?
Crumbled rock and organic matter
What needs to form before shrubs can grow?
Soil
How long can it take for sufficient soil to form?
100-1000s of years
Define secondary succession
The process of succession that occurs after an existing community is cleared by a disturbance
What type of succession occurs after a disturbance event?
Secondary
What type of succession occurs in an area devoid of life?
Primary
Is primary or secondary succession faster?
Secondary is faster
In a normal, functioning ecosystem, when does secondary succession stop?
It doesn’t
What is a disturbance?
A change in the composition and density of individuals in a community that shifts equilibrium
Give 3 examples of disturbances
Fire
Drought
Flood
Tree fall
What process does secondary succession happen in
Clear forest - herbaceous plants - woody shrubs - forest growth
What are pioneer communities?
Early stage inhabitants of a community
Which organisms start a stable ecosystem?
Pioneer communities
What are climax communities?
Final stage inhabitants
What are climax communities defined by?
Climatic factors - i.e: vegetation zones
What is late succession vegetation
mature communities that develop after early successional species
What are the mature communities that develop after early successional species
Late succession vegetation
What are major vegetation zones
Distinctive groups of plants that live between certain heights
What are the distinctive groups of plants that live between certain heights known as?
Major vegetation zones
What are seral communities?
an intermediate stage before a climax community is reached
What are the communities that appear at an intermediate stage before a climax community is reached called?
Seral communities
What do seral communities depend on?
The substratum (layer under the ground surface) and climate
What is the substratum
The layer of substance beneath the ground
What is a hydrosere?
Plant succession in an area of freshwater
What is a Lithosere?
Plant succession that begins on a newly exposed rock surface
What is a psammosere?
A seral community on a newly exposed coastal land / sand dunes
What is a xerosere?
A seral community in an area limited by water availability / extremely dry areas - i.e: sand desserts
Give 3 types of seral communities
Any from: Psammosere Xerosere Hydrosere Lithosere Halosere
What is the name for a seral community in freshwater?
Hydrosere
What is the name for a seral community in extremely dry conditions?
Xerosere
What is the name for a seral community in sandy coastal areas?
Psammosere
What is the name for a seral community on newly exposed rock?
Lithosere
What is the name of the seral community in a saline body?
Halosere
Where would you find a halosere?
Salt marshes
What is a prisere?
A collection of seres making up the development of an area
- from from non-vegetated surfaces to a climax community
What is a sere?
The seral community
when do primary and secondary AQUATIC succession occur
Primary - occurs when an area fills with water for first time
Secondary - occurs when a flood or excess nutrient runoff disturb the area
What is the process of aquatic succession?
1) Phytoplankton stage - Algae and organisms add nutrients to water body - grow and support plants
2) Root submerged stage - Soil, fallen leaves and decaying matter pile on bottom of lake - lake becomes shallow and marshy
3) Eventually lake fills in creating grassy meadow
What is aquatic succession?
When a body of water turns into land
What are mesophytes?
Terrestrial plants which are neither adapted to particularly dry nor particularly wet environments
Give an example of a mesophytic habitat
A rural temperate meadow
What are the 7 stages of a hydrosere succeeding into a climax forest community ?
1) pioneer stage
2) Submerged stage
3) Floating stage
4) Reed swap stage
5) Marsh meadow stage
6) Woodland stage
7) Climax forest community (mesophytic)
What are the 4 main stages of aquatic succession?
Phytoplankton stage
Submerged stage
Reed swap stage
sedge/ marsh meadow stage
What is the berm / strandline?
The shoreline above present water level
What is an embryo dune?
Where sand accumulation persists, perennial grasses may start to colonise and to stabilise the dune
Describe 3 features of an embryo dune
Any from: Less than 1 meter high More than 80% exposed sand Little humus or moisture High saline High wind exposure
Describe 3 features of a mobile/ yellow dune
5 meters high
~20% sand exposure
Less saline - washed by rain water
Built by marram grass that traps sand
Describe the features of fixed/ grey dunes
8-10 meters high (younger dunes)
5m high in older dunes
less than 10% exposed sand
more organic material, more nutrients, bettwe water retention
often closely grazed by rabbits, preventing shrubs
Rich plant and insect life
Name 2 grass species found in embryo dunes
Sand couch grass
Lyme grass
Name 2 grass species found in mobile / yellow dunes
Marram grass
Sea holly
Sea spurge
Name 2 plant species found in young fixed dunes
Lichens and moss
Birdsfoot trefoil
Restharrow
Name 2 plant species found in older fixed dunes
Lady’s bedstraw
Harebell
Sea buckthorn
What are Connell and Slatyer’s 1977 3 models of succession?
1) early species facilitate later species by making environment more favourable
2) early species dominate enviro and inhibit later species establishment
3) later succession species grow slower and eventually replace earlier species
What do all 3 of Connell and Slatyer’s 1977 models of succession include?
The focus of a pioneer species that produce lots of seeds, germinate early and grow quickly - (not how succession actually proceeds)
What one thing causes succession
Changes in enviro conditions
What are the two types of causes of succession?
Autogenic succession - driven by biological causes
Allogenic succession - driven by geophysical forces
What is autogenic succession?
Succession driven by biological processes that modify conditions and resources caused by the plants themselves
What does autogenic succession result in
secondary succession
What mainly causes autogenic succession?
The plants themselves
Plants cause enviro conditions to change - leads to secondary succession
What are 3 ways plants can cause autogenic succession?
Competition for space Nutrients pH changes Water uptake Shade creation
What is allogenic succession?
Succession driven by geophysical forces
What are 3 geophysical forces that can cause allogenic succession?
Floods Climate change Fires Erosion Leaching Drainage DISTURBANCES
What are the 3 factors that affect community change?
Rate of habitat modifications (i.e: rate of soil formation)
Dispersal of species
Disturbance
How can disturbance be benefical?
Can be used to maintain species composition and diversity in conservation to artificially maintain habitats
What does the intermediate disturbance hypothesis suggest?
That moderate disturbance has the greatest species diversity
Why does the intermediate disturbance hypothesis ‘work’?
because low level disturbance results in only competitively dominant species surviving
high level disturbance prevents slow grazing species establishing
Intermediate maximises diversity by opening the occupation of less competitive species
How does small scale disturbance affect community structure?
Creates of different habitats (maintains diversity)
How does large scale disturbance affect community structure?
disturbances natural part of many communities ???
