BIOL 121 Lecture Notes - Lecture 30: Lichen, Surface Mining, Intermediate Disturbance Hypothesis
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BIOL 121 Full Course Notes
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Biol 121 lecture 30 ecosystems and community dynamics. Disturbance: an event that removes some individuals or biomass from a community, categorized into pulse (short) or press (long, alters aspect of resource availability. Short term (pulse: windstorm, wave action, floods/fires, disease epidemics, new species arrivals, rapid increase in herbivore numbers. Long term (press: climate shifts, extinction of prey or mutualist, continental movements, mountain building, change in river channels. Human disturbances: deforestation, surface mining, commercial agriculture. Each community experiences a characteristic type, frequency and severity of disturbances, know as a disturbance regime. Primary succession occurs when a disturbance removes the soil and its organisms, as well as organisms living above the surface: e. g. moss, lichen, bacteria. Secondary succession occurs when a disturbance removes some or all of the organisms from an area, but leaves the soil intact.
