Ecosystems - Stability

What is resistance?

The ability of an ecosystem to remain unchanged despite disturbance

Resilience

The ability of an ecosystem to adapt / rebound from change.

What are requirements for stability in an ecosystem?

• Nutrient cycling without leakages

• High genetic diversity so populations can adapt to selection pressures

• Climate variables within tolerance limits

• Absence of human disruption

• Steady energy supply

What is a keystone species?

A species critical to the survival of other species in its ecosystem - a niche that supports the ecosystem

What is Primary succession?

Development of an environment that starts as barren, with early colonisers generating small amounts of growth which then develops into more complex communities, with increasingly complex food webs etc.

What is secondary succession?

Occurs when a disturbance has cleared away a pre-existing community, but soil is left intact.

These types of succession start, grow and end with?

Start with a pioneer species

Grow with a range of intermediate species

Ends with a climax community

What is cyclical succession?

A type of secondary succession:

Species are repeatedly being replaced over time without very large disturbances. Dominating climax communities are replaced regularly by other ones.

Arrested Succession

Is caused by human activity.

Natural progression is paused and an alternate stable community dominates ( a plagioclimax ) and succession is paused.
Eg.

• Pastoral Grazing (plant species are removed by grazing animals)

• Wetland Drainage (anaerobic conditions are drained)