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 1st STEP: Begins in a place without any soil: Sides of volcanoes Landslides Flooding 2nd STEP: Lichens that do not need soil to survive grow on rocks. Mosses grow to hold newly made soil Known as PIONEER SPECIES

What are Pioneer species? Pioneer species are a group of organisms, such as lichens, found in the primary stage of succession and that begin an area's soil-building process. MOSS FIREWEED LICHENS

Pioneer Species Low, growing moss plants trap moisture and prevent soil erosion Lichens break down rock to form soil.

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 3rd STEP: 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 4th STEP: 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

Stages of Primary Succession 1 2 3 4

Secondary Succession STEP 1: Begins in a place that already has soil and was once the home of living organisms STEPS 2-4: Occurs faster and has different pioneer species than primary succession Example: after forest fires

Secondary Succession

Secondary Succession

Stages of Secondary Succession 1 2 3 4

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

Climax Community

What are Keystone Species? Keystone species are a single species that is not usually numerous in a community but exerts strong control on the structure of the community. If the population of a keystone species declines it can have dramatic changes on the other species in the community.

Keystone Species Hunting of sea otters caused the kelp forest to nearly vanish. WHY?

Keystone Species Killing of prairie dogs by farmers caused the black-footed ferret to become nearly extinct. WHY?

Keystone Species

ANY QUESTIONS?

Succession Flow Chart ISN p. ? Divide your page into 8 boxes Make a flow chart to show the stages of: Primary Succession vs. Secondary Succession Include a description and a picture for each

Succession Flow Chart PRIMARY SUCCESSION Step 1: SECONDARY SUCCESSION