Succession.pdf

Ecological Succession Succession occurs following a disturbance in an ecosystem.  Succession regenerates or creates a community after a disturbance How do communities change over time? 2 types of Succession: Primary and Secondary Primary succession...

Ecological Succession Succession occurs following a disturbance in an ecosystem.  Succession regenerates or creates a community after a disturbance How do communities change over time? 2 types of Succession: Primary and Secondary Primary succession — started by pioneer species, such as lichens and mosses *occurs in previously uninhabited area example: when bare rock is exposed by receding glacier Secondary-started by species that remained after disaster but with soil intact Example: forest fire  Primary Succession- Begins in areas with no remnants of an older community. It occurs on bare rock surfaces where no soil exists. The first species to live in an area of primary succession are called pioneer species. After a volcanic eruption the land is cleared, organism are destroyed, and land is barren. Pioneer Species are the first organism that colonize a barren area. Lichens are a common pioneer species that works to fix the atmospheric nitrogen unto useful forms for other organisms to use. This stimulates the colonization of other species in the area. Man-made and natural disasters cause some species to die out or move on to new environments. Primary Succession Secondary Succession  Secondary succession occurs when a disturbance changes a community without completely destroying it. Not all disasters are caused by nature. Man-made disasters that affect an ecosystem are: logging, farming, overgrazing of cattle, and urbanization Secondary succession proceeds faster than primary succession because the soil layer survives and is left intact. This opportunity allows surviving vegetation to regrow and re-populate the community. After a forest fire, spared trees continue to grow and the scorch allows some seeds to be stimulated to germinate. Secondary succession occurs in areas where remnants of a previous ecosystems remain.  A climax community is a mature, relatively stable ecosystem. Secondary succession in healthy ecosystems following natural disturbances often reproduces the original climax community. Ecosystems may or may not recover from extensive human-caused disturbances. Extensive logging and deforestation may cause an ecosystem to fail to recover. As trees are downed the topsoil erodes. A loss of producer habitat will create a loss of consumer habitat. Types of Disturbances Dispersal Patterns Dispersal Patterns