Ecological Succession Changes in Ecosystems Ecological Succession

Definition of Ecological Succession Transition in species composition taking place in a given area over ecological time Natural, gradual changes in the types of species that live in an area The gradual replacement of one plant community by another through natural processes over time

Primary Succession Begins in a place without any soil (parent material – bedrock to start) Sides of volcanoes Landslides Flooding Glacier melt Starts with the arrival of living things such as lichens that do not need soil to survive Called PIONEER SPECIES

A Candidate for Primary Succession

Another Candidate for Primary Succession

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

Primary Succession Simple plants like mosses and ferns can grow in the new soil

Primary Succession The simple plants die, adding more organic material 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 in 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 Forest fires Floods, hurricanes, tsunamis Human destruction – clear cutting, abandoned agriculture fields

Secondary Succession Begins

Secondary Succession Ecosystems undergo secondary succession following artificial or natural disturbance such as a forest fire or farming. In 1850, Connecticut was almost entirely open land cleared for farming or timber. Today, Connecticut has been mostly reforested through the process of secondary succession as farming has left the state since the 1800's.

Climax Community An ecological community in which populations of plants or animals remain stable and exist in balance with each other and their environment. A climax community is the final stage of succession, remaining relatively unchanged until destroyed by an event such as fire or human interference. Does not always mean big trees Grasses in prairies Cacti in deserts

Succession In the background are the trees of an eastern hardwood forest. This area has not been cleared in over fifty years. These trees represent the climax community for the rainfall, temperature and soil of this area.

Succession The area on the right, behind the fence, in front of the trees, has not been mowed in about ten years. Shrubs and evergreen trees have moved in. These are the intermediate species.

Succession The area in the foreground, in front of the barbed wire fence, has been mowed within the last year. The plants are all annuals or herbaceous perennials. These are the pioneer species.