Disturbance and succession Flashcards
What is meant by stability?
tendency of a community to maintain a constant composition and number of species in the face of disturbance
What is the Nonequilibrium model
Communities are subject to constant change because of disturbance and ecological succession
examples of disturbances
Storms and fires
Examples of ecological succession
Predictable change in the species that occur associated with changes in the abiotic environment
How does disturbances influence species diversity and composition?
- Natural and human disturbances
- Modification of environment for building
- Livestock grazing
- Shipwrecks
4 ways of categorising the responses of ecological communities to disturbance:
- Fragility
- Robustness
- Resilience
- Resistance
What is fragility?
A fragile community is unchanged by minor disturbances but are dramatically altered by major disturbances
What is robustness?
A robust community is largely unchanged even during major disturbances
what is resilience?
Resilient communities rapidly return to their former structure following disturbances
What is resistance?
Communities undergo relatively little change in the face of disturbance
Disturbance isn’t always bad - why?
Moderate levels of disturbance create conditions that foster high diversity
e.g increase habitat diversity (increase niches available) and disrupt competitive dominance and exclusion
Frequent small-scale disturbances…
help prevent large scale disturbances
What is the intermediate disturbance hypothesis?
Moderate disturbance maximises species richness and biodiversity
What is primary succession?
Occurs when a new area is colonised for the first time
Microbes, lichens and mosses
These colonisers key to soil formation
What is secondary succession?
Occurs when existing communities are disturbed, but soils remain intact
Fires or agricultural clearance
Communities will often return to former state
