2.7 Changes in Ecosystems: Ecological Succession

Natural, gradual changes in the types of species that live in an area; can be primary or secondary
The gradual replacement of one plant community by another through natural processes over time

Begins in a place without any soil
- Sides of volcanoes
- Landslides
- Flooding
Starts with the arrival of airborne pioneer species such as lichens that do not need soil
Soil starts to form as lichens, weather and erosion break down rock
When lichens die, they decompose, adding small amounts of organic matter to the rock to make soil
Simple plants like mosses and ferns can grow in the new soil
The simple plants die, adding more organic material
The soil layer thickens, and grasses, wildflowers, and other plants begin to take over
These plants die, and they add more nutrients to the soil
Shrubs and tress can survive now
Insects, small birds, and mammals have begun to move in
What was once bare rock now supports a variety of life

Begins in a place that already has soil and was once the home of living organisms
Occurs faster and has different pioneer species than primary succession
Example: after forest fires

A stable group of plants and animals that is the end result of the succession process

^^Indicator species:^^ give early warning signs of damage or danger to a community

^^Keystone species:^^ have a larger impact on the community, if removed, than other species

Pollinators
Apex predators
Decomposers
specific ex: sea otter
- feed on sea urchins, controlling their population
- urchins would deplete the habitat's kelp
- Kelp is the producer; the major source of food and shelter for the ecosystem.

What happens when you lose a keystone species?