Power11_EcosystemsEnergyFlow - Ecosystem fluxes and cycles...

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1 Ecosystem fluxes and cycles • Carbon, P, and N cycles • Ecosystem “efficiency” • Toxins and bioaccumulation • Water management issues • Translocations of nutrients by organisms 2 Ecosystem ecology • Energy flows and nutrients cycle through ecosystems • Humans increasingly are changing biogeochemic al cycles and spatial distributions of storage 3 Materials cycle —atoms (H, O, C, N, Ca, P ) created in stars, used again and again, end up in different pools, fluxes transfer atoms between pools. Stocks (pools, compartments) and flows (fluxes) Input - Output = Change in Storage (= 0 at equilibrium) Turnover time : if system is in equilibrium so input (vol time -1 ) = output (vol time -1 ) = q, residence time or turnover time, T = Volume/q storage input output Energy flows— a small fraction of solar radiation is fixed by photosynthetic organisms, but once energy is dissipated as heat, it is never recovered by ecosystem (except as passive energy savings for transport—e.g. ocean or air currents driven by heat and used by organisms). storage input output Yellow system has shorter turnover time than blue system. 4 Terrestrial (bottom-heavy) pyramid of trophic level biomass 5 Freshwater and Marine: Inverted pyramids of trophic level biomass suppress sustain 6 Eutrophied lake, Queensland, Australia
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7 “Bottom heavy” trophic pyramid dominated by Cyanobacteria 8 stabilized or maintained by: *nutrient sequestration in long- lived top predators; *upslope vectoring of nutrients by mobile scavengers and predators (salmonids, birds, bats, bears) *terrestrial vegetative cover;
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This note was uploaded on 04/01/2008 for the course BIO 1B taught by Professor Carlson,mischel,power during the Fall '07 term at University of California, Berkeley.

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Power11_EcosystemsEnergyFlow - Ecosystem fluxes and cycles...

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