Changes in Ecosystems:Ecological Succession

Definition:

• Natural, gradual changes in the types of plant species that live in an area. Plant communities change in a predictable, natural process over time.

• Varies by what region you live…

• Ex: Michigan vs. Florida

Primary Succession

• Begins in a place without any soil or life– Volcanoes– Sand Dunes

• Starts with the arrival of living things such as Lichens or Dune Grass that do not need soil to survive

• Called PIONEER SPECIES

http://botit.botany.wisc.edu

Lichens: (mix of algae and fungus) secrete acids that break down rock, wood into soil.

Pioneer Species

The process starts at the beach…Dune grass grows where nothing else can. Poor soil conditions, erosion, etc.

Dune Grass Stage

• Dune grass - Pioneer Species

• First to grow in an area. Grows with little nutrients, anchors dune and it’s life cycle adds nutrients to sand to help form soil.

Edge Transition zone• Sand starting to be turned into soil through plant decay. More plant diversity/Stability

Other plants take over dune grass

EX: Beach Pea, Milkweed

Poison ivy, other grasses.

Shrub layer

• Soil is rich enough for woody plants and vines like: Stag-horn sumac, Mt. Grape, raspberry and ferns. All food for animals…

Fast Growing Trees

• Soil gets deeper (more hummus) darker organic nutrients. Fast growing species become established. Increase habitat structure and food (Stability). Species: Eastern cottonwood (poplars), wild fruit trees )(Wild cherry and plum).

Pine Trees

• Pine trees grow slow and need lots of sun.

• Out-compete faster growing trees by reducing the pH and making the soil acidic. Species: White Pine, white and black Spruce, Hemlock, Red Pine. More

Food.

Oaks

• Oaks have deep roots that go down to the aquifer, like acid soils and grow better in shade (leaf structure). Leaves acidic make nests. Acorns have protein to

support large herbivores…

Maples and Beech trees

• These hardwood species require the best soil and form the Climax stage of succession. They increase the vertical habitat and food.

Decomposers

Cycle nutrients for the plants and help form the soil. They provide food as well..

Fungi, Mosses, Lichens,

Primary Succession

• Soil starts to form as lichens and the forces of weather and erosion help break down rocks into smaller pieces

• When lichens and plants die, they decompose, adding small amounts of organic matter to the rock to make soil

http://www.life.uiuc.edu

Animal Communities

• Insects, small birds, and mammals have begun to move in

• What was once barren now supports a lot of biodiversity.

http://www.rowan.edu

Habitats at Different Levels

• Grasses : two layers ( litter and foliage)

• Shrubs: three layers ( litter, foliage, shrub canopy)

Climax Forests: relatively stable conditions, the top of the plant succession. Five or six layers of habitat (litter, microhabitat (rotten log), foliage layer, shrub canopy, canopy.

Secondary Succession

• Begins in a place that already has soil and organisms. It is regrowth after a disturbance.

• Occurs faster because soil is better.

• Example: after forest fires

http://www.geo.arizona.edu

http://www.ux1.eiu.edu

http://www.agen.ufl.edu

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– Greatest diversity/stability