Component 1.5 - Community And Succession Flashcards
What is a climax community?
A stable self-perpetuating community that has reached equilibrium with its environment and no further changes occur
What is primary succession?
The change in structure and species composition of a community over time in an area that has not previously been colonised
Give an example of where primary succession might occur?
Bare rock or the site of a volcanic eruption
What is a seral stage?
The different stages in a succession when particular communities dominate are known as seral stages.
Describe the sequence of primary succession
1) Pioneer species
2) Lichens erode rock and dead matter accumulates (primitive soil) - ants, spiders and mites can survive
3) Windblown spores allow mosses to grow, soil develops and herbaceous plants outcompete mosses - nematodes and 2
4) Tall grasses allow shade tolerant species to become established
5) As these plants decay, soil becomes thicker, humus allows it to hold water more efficiently, shrubs and small trees outcompete herbaceous plants
6) Soil deepens, increase in minerals and humus, over time large trees outcompete small trees and shrubs
Describe the characteristics of a climax community
1) Has great species diversity - invertebrates and vertebrates
2) Has a complex food web
3) Is dominated by long-lived plants
4) Stable
Why may plant diversity in a climax community decrease slightly from its pre-climax state?
The tree canopy limits the intensity of light reaching the woodland floor
How is a climax community in equilibrium
1) Between GPP and total respiration
2) Energy used in sunlight and released by decomposition
3) Uptake of nutrients from soil and return by decay of plants and animals
What is secondary succession?
The changes in a community following the disturbance or damage to a colonised habitat
Why are secondary successions not all the same?
- depends on condition prior to disturbance e.g soil thickness, minerals and humus
- May be seeds, spores, bulbs in ground
Describe how humans can prevent the development of a climax community
- Grazing by sheep and cattle (prevents shrubs and trees)
- Farming of land removes all except deliberately introduced species
- Deforestation removes community of larger trees
How are heather Moore managed to provide ideal conditions for game birds?
- Management is carried out mainly by burning
- Pioneer phase supplies the best food for adult grouse (feed mainly on young, succulent heather shoots)
- Building phase provides best shelter for nesting
- Without management the heather would pass through mature phase and degenerate (not correct conditions for breeding of grouse)
How does migration effect succession?
Immigrating non-native species may spread widely altering the community and soil
Define a niche
The role and position a species has in its environment including all interactions with the biotic and abiotic factors
Describe how interspecific competition plays a role in population size?
Different species have common needs but each has its own niche. In the long term two species can occupy the same niche in a specific habitat. Whichever has the competitive advantage at the time may survive.
