Power11b_DisturbanceFoodChainNotes - drought: 40-90...

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1 Disturbance and food chain length 1. Strength (sometimes the sign) of food web interactions are context dependent. 2. Disturbance can lengthen food chains by resetting lower trophic levels to early successional states dominated by more edible taxa. 3. Diet doesn’t predict dynamics. Top down control pathways can differ from energy flow bottom up pathways in the same food web. 2 4 levels: barren 3 levels: green, and nitrogen limited (Hairston et al. 1960 Fretwell 1977) 3 1990,1991: Roach, Steelhead, Both, Neither (6 replicates) Algae collapsed to detritus in all treatments ! 4 Big armored caddisfly grazer: Dicosmoecus gilvipes ( indiv / sq. m) flood: 0-1
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Unformatted text preview: drought: 40-90 Drought: no scouring winter floods 5 D i c o s m e u-+ Wootton, Parker and Power 1996, Science Experimental Treatments (N = 6): Dicosmoecus (+, -) x Steelhead (+, -) 6 6 6 6 Steelhead: + -6 Dicosmoecus No No Dicosmoecus Dicosmoecus 7 Defended (armored or sessile) grazers dominate downstream from dams or diversions, where flow is artificially regulated 8 Natural Disturbance vs Artificial Regulation Flood: Edible grazers Drought: Inedible grazers 9 Diet doesnt predict dynamics!! Top down cascade through four trophic levels Bottom up energy flow through three trophic levels...
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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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Power11b_DisturbanceFoodChainNotes - drought: 40-90...

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