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Ecological Succession Succession • series of predictable changes that occur in a community over time. • Changes begin as the result of a disturbance or the appearance of new habitat. Types of Succession • 2 Categories – Primary Succession – Secondary Succession Primary succession • Development and change of communities on land where no ecosystem existed before • Slower- 100-1000 yrs • e.g., lava flows, glacial retreats, city streets Primary Succession • Begins in a place without any soil – Sides of volcanoes – Landslides – Areas left after glaciers recede • Starts with the arrival of living things such as lichens that do not need soil to survive • Called PIONEER SPECIES Pioneer species • First organisms to colonize newly available areas and begin soil formation and/or succession • e.g., lichens on bare rock, fireweed on disturbed land Pioneer Organisms 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 http://www.life.uiuc.edu Primary Succession • Simple plants like mosses and ferns can grow in the new soil that was formed from the lichens http://www.uncw.edu http://uisstc.georgetown.e du Primary Succession • The simple plants die, adding more organic material • The soil layer thickens, and grasses, wildflowers, and other plants begin to take over http://www.cwrl.utexas.edu Primary Succession • These plants die, and they add more nutrients to the soil • Shrubs and tress can survive now http://www.rowan.edu Primary Succession • Insects, small birds, and mammals have begun to move in • What was once bare rock now supports a variety of life http://p2-raw.greenpeace.org Terrestrial Primary Succession Climax community • The final, stable community that forms on undisturbed land… the end-product of succession • Climax communities do not continue to change very muchthey are stable systems • Not always large trees- different climax community in each ecosystem Secondary succession • Change in communities following a disturbance or alteration of the previously existing community • e.g., forest fires, ponds, fallow fields • Occurs much more quickly than primary succession