CM L2 Flashcards
Agents of change can be?
Biotic or abiotic
Abiotic agents of change can be of two types
Disturbances and stresses
Disturbance
An abiotic event that physically injures or kills some individuals and creates opportunities for other individuals to grow and reproduce
Stress
Occurs when some abiotic factors reduce the growth, reproduction or survival of individuals and creates opportunities for other individuals
How do disturbance and stress affect succession
Disturbance and stress play critical roles in driving succession
Succession
The process by which the species composition of a community changes over time
Primary succession
The colonization of habitats that are devoid of life due to catastrophic disturbance Or because they are new habitats
Secondary succession
The reestablishment of a community in which most but not all of the organisms have been destroyed
Melting of glaciers in Glacier Bay, Alaska has led to
A sequence of community change that reflects succession over many centuries
Once a new habitat is exposed, what develops first?
A primary/ pioneer stage dominated by lichens, mosses, horsetails, willow and cottonwoods
Second community
Dryas stage
Third community
Alders stage(alders dominate)
Key findings of secondary succession after Mt.St. Helen’s eruption
- Eruption survivors are key drivers of ecosystem rebirth and initiate major changes early in the post-eruption period
- Animal disturbance disturbs seed bank beneath ash layer triggering germination of seedlings
- Nitrogen-fixing plants with deep rhizomes provide nutrient cycling service for new seedlings.
When did vegetation in Ireland begin?
The end of the Pleistocene Glaciation c.15000 years ago
What are peatlands?
Climax vegetation types that expand over existing habitats.
