Ecological Succession Flashcards
What is succession?
The changes in an ecosystem over time, in the species that occupy a specific area.
What is the first stage of succession?
The colonisation of an inhospitable environment.
What are the features of pioneer species?
- The production of vast quantities of wind-dispersed seeds or spores, so they can easily reach isolated situations such as volcanic islands.
- Rabid germination of seeds on arrival as they do not require a period of dormancy.
- The ability to photosynthesise, as light is normally available but other “food” is not. They are therefore not independent on animal species.
- The ability to fix nitrogen from the atmosphere because, even if there is soil, it has dew or no nutrients.
- Tolerance to extreme conditions.
How does succession work (affect species)?
Takes place in a series of stages. At each stage, certain species can be identified which change the environment, especially the soil, so that it becomes more suitable for other species. These other species may then out-compete the species in the existing community and so new community is formed.
What is a climax community?
Stable state comprising a balanced equilibrium of species with few, if any, new species replacing those that have become established.
What are the common features that emerge in succession.
- The non-living environment becomes less hostile- e.g. soil forms, nutrients are more plentiful and plants provide shelter from wind. This leads to:
- A greater number and variety of habitats, that in turn produces:
- Increased biodiversity- as different species occupy these habitats. Especially evident in early stages, reaching peak in mid-succession, but decreasing as the climate community is reached. Decrease is due to dominant species out competing pioneer and other species, leading to their elimination from the community. With increased biodiversity comes:
- More complex food webs, leading to:
- Increased biomass, especially during mid-succession.
What alternatively causes succession?
When land that has already sustained life is suddenly altered. This may be the result of land clearance for agriculture or a forest fire. Normally occurs more rapidly.
Why does succession in an already sustained environment occur more rapidly?
Spores and seeds remain alive in the soil, and there is an influx of animals and plants through dispersal and migration from the surrounding area.
What are the stages of succession?
Barren land(hostile conditions, low species diversity and instability) -> Primary colonisers (lichen)-> Secondary colonisers (mosses) -> Tertiary colonisers (grasses)-> Scrubland (shrubs) ->Climatic climax (woodland)(Less hostile conditions, high species diversity and stability)
What is conservation?
The management of the Earth’s natural resources in such a way that maximum use of them can be made in the future.
Involves active intervention by humans to maintain ecosystems and biodiversity. It is therefore a dynamic process that entails careful management of existing resources and reclamation of those already damaged by human activities.
What are the main reasons for conservation?
Ethical: Other species should coexist with us. Respect.
Economic: Valuable use of species.
Cultural and Aesthetic: Habitats and organisms enrich our lives.
How can you conserve a habitat by managing succession?
Habitats disappear as a result of succession, or they have been out-competed by other species. So manage succession in a way that prevents a change to next stage.
