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Transcript
Ecosystem Responses to Disturbance Ecological succession Disturbance and resilience Evolving ecosystems Equilibrium Theory Ecosystems are stable environments in which the biotic interactions among species determine the structure of the communities present. Succession and Disturbance Ecological succession: transition between biotic communities Primary: no previous biotic community Secondary: previously occupied by a community Aquatic: transition from pond or lake to terrestrial community Primary Succession Mosses invade an area and provide a place for soil to accumulate. Larger plants germinate in the new soil layer, resulting in additional soil formation. Eventually shrubs and trees will invade the area. Primary Succession Secondary Succession Soil present Most of the biotic community destroyed Human development Landslides Fire Secondary Succession Growth of Climax Ecosystem limited Erosion of soil Drought High temperature Secondary Succession Aquatic Succession Fresh water aquatic ecosystem develops into a terrestrial ecosystem Sediment and detritus fills in pond or lake Amount of water decrease Meadow is often a transitional stage Climax community bog or forest Aquatic Succession Disturbance and Resilience Removes organisms Reduces populations Creates opportunities for other species to colonize Ground Fire Fire and Succession Fire climax ecosystems: dependent upon fire for maintenance of existing balance; e.g., grasslands, pine and redwood forests Forest management necessary Burn off brush and debris on forest floor Germination of new trees Reintroduce nutrients into soil