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Topic+16.+Productivity+and+energy+flow - Topic 16...

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Topic 16: Productivity and Energy Flow I. Kinds of productivity A. Energy is brought into the web by green plants and goes up web at some rate. Each level produces new growth and/or new individuals; energy is also used in the metabolism of organisms at each level. This goes under the heading of productivity , and there are two kinds of productivity (2 Defs): 1. Gross primary productivity (GPP): Rate at which energy is bound/organic matter created by producers via photosynthesis. The fraction of sunlight captured is <2 %. The plants metabolize some of the GPP and the rest goes into biomass (body of plant) and gets eaten by herbivores or eventually decomposers. Herbivores are eaten by carnivores, etc. 2. Net primary productivity : Gross primary productivity minus plant metabolic rate (= plant respiration). B. Units of productivity: mass (or energy)/area-time. It is a rate, so per time, and like density is per-area (or per volume). II. Example of productivity measures: Oak-pine forest of Long Island, NY. Whittaker and Woodwell. Gross primary productivity = 2650 g/m 2 /yr Plant metabolism = 1450 Net primary productivity = 1200 Of this 1200, Decomposer metabolism = 580 Other organisms’ = 80 Biomass accumulation = 540 of all organisms, including plants When the biomass accumulation = 0, no increase in weight of organic tissue (= biomass) per area occurs.
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III. Conditions favoring high productivity A. 3 conditions: 1. high temperature 2. lots of water 3. lots of nutrients B. Where are all these found?
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