Succession Flashcards
What is succession
The process by which an ecosystem changes over time
The biotic conditions change as the abiotic conditions change
What are the stages of succession called
Seres
What are the two types of succession
Primary succession
Secondary succession
Where does primary succession occur
Happens On land that’s been newly formed or exposed e.g.where a volcano erupts and forms a new rock surface
Describe the characteristics of primary succession
- abiotic conditions are harsh e.g. No soil to retain water
- seeds and spores are blown in by wind
What is the name of the first species to colonise the area
Pioneer species
This is the first sere
How do pioneer species grow first?
They’re specialised to cope with the harsh conditions
e.g. Marram grass can grow on dunes by sea as they have deep roots to get water and can tolerate salty waters
How do pioneer species change the abiotic conditions in a primary succession
They die and decompose which forms basic soil
What happens once basic soils are made
Conditions become less hostile - basic soil helps retain water which means new organisms can grow. Then die and decompose adding more organic material making the soul deeper and richer in minerals, means larger plants like shrubs can start to grow in deeper soil (retains even more soil)
Where does secondary succession occur
Happens on land that’s been cleared of all the plants but the soil remains e.g. After a forest fire
Describe secondary succession
Happens in the same way as primary succession, but soil is already there so succession starts at a later Sere.
Pioneer species in secondary succession are larger plants e.g. Shrubs
How do dominant species occur in the ecosystem
At each stage the different plants and animals that are better adapted for improved conditions move in and out compete the plants and animals already there
What happens as succession occurs
An ecosystem becomes more complex, new species move in alongside existing species which means the species diversity increases
What is the final sere of a succession
Climatic climax
What is the climatic climax
When the ecosystem us supporting the largest and most complex community it can and the biotic and abiotic figures are in balance
What determines the route of succession
The Abiotic conditions at the start of the process
E.g.
Lithosere - occurs of exposed rock
Psammosere - on sand
Hydrosere - on water
What is a succession on a Lithosere
Bare rock to woodland
What is the first step of succession for a Lithosere
- Pioneer species (e.g. lichens) colonise the rocks as they can live with very little water and nutrients.
- lichens break down rock releasing minerals
- surface becomes uneven when rock is broken, helps retain water
What happens after the rock has been broken down in a Lithosere
Rocks get damp so mosses begin to grow and weather the rock surface.
Lichens and misses die and decompose forming thin soil
What happens after the soil is beginning to appear in a Lithosere
Soil deepens, larger plants that need more water move in (e.g. grasses, fern, herbs and flowering plants)
Soil gets deeper as larger plants die and are decomposed by bacteria to form humus
What happens after the larger plants begin to decompose?
Shrubs, ferns and small trees (birch) begin to grow.
They out-compete smaller plants to become dominant species
What happens in the last stage of succession on a Lithosere
Soil is deep and rich in nutrients to support slow growing large trees (ash, oak)
Become dominant species and the climax community is formed
