refers to the sequence beginning in an area where there is no soil or previous forms of life lava field newly formed sand dune

Transcription

1 Succession: Ecological succession refers to a series of changes that every community undergoes over long periods of time. The process of succession begins with relatively few pioneering plants and the animals associated with these plants. The succession in plant life is paralleled by succession in animal life. The organisms that make up the primitive community gradually change the environmental conditions so each successive community paves the way for the next. Each successive community develops through increasing complexity until it becomes a final, sustainable, stable, or self perpetuating community, of dominant organisms, known as a climax community. In an ecosystem with a climax community, the conditions continue to be suitable for all the members of the community. The climax community is the final stage of ecological succession.

2 The stages of succession: Primary Succession Secondary Succession Primary Succession: refers to the sequence beginning in an area where there is no soil or previous forms of life lava field newly formed sand dune

3 very slow process because it must start with the formation of soil soil forms as a result of weathering and pioneer organisms such as bacteria, fungi and lichens pioneer species the first type of life to inhabit an area pioneer species add organic matter to the primitive soil, changing conditions so mosses, ferns and other primitive plants take over grasses may eventually replace the primitive plants making the soil even richer shrubs grow and shade the grass causing it to die then trees grow and shade out the shrubs one community of trees will be succeeded by another community with different trees this process will continue until a dominant or climax community is established or another disturbance occurs

4 Secondary Succession: occurs in an area in which an existing community has been partially destroyed and its balance upset by natural causes or as a result of human activity fires logging abandoned farm

5 difference between primary and secondary succession is that in secondary succession the soil already exists secondary succession starts with dormant seeds already in the soil or seeds that come from plants in nearby communities these seeds will establish a community and then succession will eventually result in a climax community an abandoned farm will most likely become a forest the final climax community is generally the same as the climax community that surrounds the disturbed area Factors that contribute to ecological succession: The type of climax community that is established will depend on the environmental conditions of the area. The most important environmental conditions that affect succession include: climate (temperature, precipitation, sunlight) soil (salinity, fertility, moisture, texture) geographical features (latitude, altitude, proximity to mountain ranges and/or large bodies of water)

6 The cause of change include: Natural causes: flood fires volcanic activity climate change(*) species extinction(*) Human Influenced: acid rain ozone depletion pollution habitat destruction mono culture farming clear cutting over fishing

7 Every ecosystem exists in a balance between its members (producers, consumers, decomposers, etc.) and its abiotic factors. This balance between the biotic and abiotic factors creates stability in the ecosystem. The greater the biodiversity, the greater the stability. Even with this stability, ecosystems are relatively fragile. A change in the balance can stress an ecosystem leading to its destruction. In order to sustain a global balance, we must take responsibility in maintaining the stability of ecosystem. Allowing natural changes and succession to occur while managing or eliminating human influenced changes to ecosystems.

8 Read "Changes and Stability in Ecosystems" on p Answer the following questions: What does equilibrium mean in terms of a forest ecosystem? Identify at least four conditions which help maintain equilibrium in a forest ecosystem. In what ways have humans affected natural ecosystems such as a forest or large lake? What are some of the human activities in your area that are having a negative impact on an ecosystem near you? What can be done to help your local ecosystem recover?