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Changes in Ecosystems:Ecological Succession
What is 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
Primary Succession
• Begins in a place without any soil: »Sides of volcanoes
»Landslides
»Flooding
• First, lichens that do not need soil to survive grow on rocks
• Next, mosses grow to hold newly made soil
• Known as PIONEER SPECIES
Pioneer Species
Lichens break down rock to form soil.
Low, growing moss plants trap moisture
and prevent soil erosion
Primary Succession
• Soil starts to form as lichens and the forces of weather and erosion help break down rocks into smaller pieces
• When lichens die, they decompose, adding small amounts of organic matter to the rock to make soil
Primary Succession
• Simple plants like mosses and ferns can grow in the new soil
Primary Succession
• The simple plants die, adding more organic material (nutrients to the soil)
• The soil layer thickens, and grasses, wildflowers, and other plants begin to take over
Primary Succession
• These plants die, and they add more nutrients to the soil
• Shrubs and trees can survive now
Primary Succession
• Insects, small birds, and mammals have begun to move into the area
• What was once bare rock, now supports a variety of life
Secondary Succession
• 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
Climax Community
• A stable group of plants and animals that is the end result of the succession process
• Does not always mean big trees
–Grasses in prairies
–Cacti in deserts
How ecosystems change? Seasonal changes
can affect ecosystems.
All organisms depend
on resources from their
environment for
survival.
Climate Change –
Drastic changes to the
Earth’s temperatures
over many years.
How ecosystems change?Natural disasters
can affect
ecosystems.
Earthquakes
Volcanoes
Hurricanes
Tornadoes
Wild Fires
Floods/Storm
surges
Mount St. Helens eruption destroy entire
ecosystems. 32 years later is all back.
How ecosystems change? Human intervention can
affect ecosystems.Urban development
Oil spills
Canals in Miami
(diverging water from the
Everglades)
Land Fills
Deforestation
Which one is easier for
ecosystems to return from:
human intervention or
natural disasters?
How are succession communities
different?Pioneer Community
Harsh environment.
Biomass increasing.
Energy consumption
inefficient.
Some nutrient loss.
Low species diversity.
Fluctuations common
Little stability
Climax Community
Most favorable
environment.
Biomass stable.
Energy consumption
efficient.
Nutrient cycling.
High species diversity.
Fluctuations do not usually
occur.
Great stability.