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Transcript
Succession We will: describe the different types of ecological succession You will: develop an understanding of succession and how ecosystems are constantly changing. Ecological Succession Definition: series of gradual changes that occur in a community following a disturbance. Primary Succession Succession that begins in these areas that have no remnants of an older community Primary Succession Example In Glacier Bay, Alaska, a retreating glacier exposed barren rock. Over the course of more than 100 years, a series of changes has led to the hemlock and spruce forest currently found in the area. Changes in this community will continue for centuries Pioneer Species The first species to colonize barren areas Barren = bleak and lifeless Named after rugged human pioneers who first settle wilderness areas Pioneer Species that do the literal, ground-breaking work that makes an area habitable for subsequent settlers. Secondary Succession When a disturbance affects an existing community but doesn’t completely destroy it. Proceeds faster than primary succession, in part because bits of the old community, and can regrow rapidly When does Secondary Succession Occur? Wildfire/Forest (Fire Fires can stimulate their seeds to germinate) Hurricanes Other natural disturbance Human activity Example: Logging and farming Secondary Succession Example This series shows changes taking place in abandoned fields of the Carolinas’ Piedmont. Over the last century, these fields have passed through several stages and matured into oak forest. Changes will continue for years to come. Process during Succession Every As organism changes its environment succession continues species diversity usually increases Do ecosystems return to “normal” following a disturbance? Succession doesn’t always follow the same path, and that climax communities are often not uniform and stable. Succession after Natural Disturbance Natural Storm Think disturbances damage, wildfires, etc. quilts! Natural disturbances usually disturb patches of communities at different times Different patches may be in a different stage of secondary succession Secondary Succession Secondary succession occurred since soil and few plants remained in the area after the storm. Succession after Human-Caused Disturbance Land cleared for farming then abandoned Ecosystems may or may not recover from extensive human-caused disturbances. Example: Clearing and farming of tropical rain forests, can change the structure and community of microorganisms in soil in ways that prevent regrowth of the original community. THE BIG PICTURE Communities change over time because of natural or human disturbances and because organisms alter their environment and pave the way for other species. Example: When trees grow in an area, they provide shade and cooler temperatures near the ground, allowing shadeloving organisms to move in.
