Succession

Responses to disturbance 1. A community may resist change & remain stable (resistant) 2. A community may change in response to the disturbance but later return to its original state (resilience) 3. A community may be modified from the disturbance and never return to its original state

Natural Disturbances Man-Induced Mortality Tree-fall Wildfire Volcano Flooding Hurricanes/tornadoes Insect/disease Tsunami Landslides Glaciers Sea-level rise or retreat Logging Plowing Mining Dam Removal Fire/Flooding Nuclear blast/warfare

What happens when a disturbance is severe enough it eliminates all or most of the species in a community?

Ecological Succession It will undergo a somewhat predictable series of changes called succession

Primary Succession Follows a disturbance so severe that no vegetation or soil life remains from the community that once occupied the site The biotic community has to rebuild from scratch Can be caused by… Sides of volcanoes Landslides Glacier retreats Lakes dries up

Pioneer Species: Lichen

Pioneer Species Pioneer species have spores and seeds that can travel long distances Lichens: secrete acids that break down rock, forming soil Once soil is in place, small plants, insects & worms have suitable habitats

Primary succession Species diversity increases as time passes

Secondary Succession Begins when a disturbance dramatically alters an existing community but does not destroy all living things or all organic matter in the soil. Parts of the community remain, and become building blocks Examples: Abandoned farmlands Burned (fire) or cut forests (logging) Hurricane Flooding Heavily polluted streams

Secondary Succession Recovers faster and has different pioneer species than primary succession (no need for lichen)

Succession in an Aquatic Biome Aquatic: transition from pond or lake to terrestrial community (bog or a forest)

Climax community Will remain in place with little modification until some disturbance restarts succession

Intermediate disturbance hypothesis: Communities that experience fairly frequent, moderate disturbances have the greatest diversity of species Removes organisms Reduces populations Creates opportunities for other species to colonize

some communities never return to climax state- too disturbed by human impact

Restoration Ecology Restoration Ecology= restoring damaged areas to their pristine environment (what they once looked like) Difficult Time consuming Expensive Doesn’t always work *Best to protect natural systems from human degradation

Florida Everglades

Chesapeake Bay Too much N, P, and sediment. Restoration of wetlands, oyster reefs, reopening fish passages