1Lecture 18 Productivity andLecture 18 Productivity andFood WebsFood WebsPhotosynthesis and Respiration on ecosystemPhotosynthesis and Respiration on ecosystemscalesscalesAnalysis of global productivityAnalysis of global productivityEnergy flow through Energy flow through trophictrophic levels and levels andecosystemsecosystemsThree weeks in the life of a food web (DVD)Three weeks in the life of a food web (DVD)World Net Primary Productivity(Rounded Estimates) Ecosystem NPP (g m-2 y-1) World NPP (x1015 g y-1) Biomass (g m-2 ) World Biomass (x1015 g ) Desert 80 0.5 720 15 Grassland, etc. 500 18 4000 125 Cultivated Land 760 8 1000 14 Moist Forest 1000 1230,000 900 Tropical Forest 2000 18 45,000 750 LAND TOTAL 1804 Estuaries 2000 3 1500 2.6 Continental Shelf 500 5 20 .3 Open Ocean 100 40 3 1.0 MARINE TOTAL 48 3.9 World NPP = NPP × ∑AreaWorld Biomass = Biomass × ∑Area561015g = 1 Gigatonsee Fig. 55.4see Fig. 55.4in your textin your textbookbookWorld Net Primary Productivity(Rounded Estimates) Ecosystem NPP (g m-2 y-1) World NPP (x1015 g y-1) Biomass (g m-2 ) World Biomass (x1015 g ) Desert 80 0.5 720 15 Grassland, etc. 500 18 4000 125 Cultivated Land 760 8 1000 14 Moist Forest 1000 1230,000 900 Tropical Forest 2000 18 45,000 750 LAND TOTAL 1804 Estuaries 2000 3 1500 2.6 Continental Shelf 500 5 20 .3 Open Ocean 100 40 3 1.0 MARINE TOTAL 48 3.9 World NPP = NPP × ∑AreaWorld Biomass = Biomass × ∑Area56World Net Primary Productivity(Rounded Estimates) Ecosystem NPP (g m-2 y-1) World NPP (x1015 g y-1) Biomass (g m-2 ) World Biomass (x1015 g ) Desert 80 0.5 720 15 Grassland, etc. 500 18 4000 125 Cultivated Land 760 8 1000 14 Moist Forest 1000 1230,000 900 Tropical Forest 2000 18 45,000 750 LAND TOTAL 1804 Estuaries 2000 3 1500 2.6 Continental Shelf 500 5 20 .3 Open Ocean 100 40 3 1.0 MARINE TOTAL 48 3.9 World NPP = NPP × ∑AreaWorld Biomass = Biomass × ∑Area563.3%3.3%65%65%% of surface% of surface2PhytoplanktonBarnacleBlue CrabSea BassZooplanktonSea WormsShore BirdsShore ShrimpMarine Food WebPhoto Source: The Lloyd Center at UMassDetritusFlow of Carbon (Energy) Through aFlow of Carbon (Energy) Through aTrophic Level (or organism)Trophic Level (or organism)RnInPn -1PnAnFnDnBnLivingBiomassDeadOrganicMatterPn-1 = Productivity of trophic level n-1Dn = Portion of Pn-1 not consumedIn = Amount IngestedFn = Fecal matter producedAn = Amount assimilated and availableRn = RespirationBn = Biomass in trophic level nPn = Productivity at trophic level nTo DetritusFood WebTrophicLevel nRnInPn -1PnAnFnDnBnLivingBiomassTrophicLevel nDeadOrganicMatterTo DetritusFood WebEfficienciesEfficienciesAssim ilationEff iciency( AE)AE= An/In×1 0 0Pro ductionEff iciency( PE)PE= Pn/An×1 0 0Ecological Efficiency = (EE)(AE)(PE)(trophic transfer efficiency) = Pn / Pn-1 × 100≈ 10 % to 20 %Exp loitat ionEff iciency( EE)EE= In/Pn-1 ×1 0 0PhytoplanktonBarnacleBlue CrabSea BassZooplanktonSea WormsShore BirdsShore ShrimpMarine Food WebPhoto Source: The Lloyd Center at UMassDetritus3PhytoplanktonZooplanktonSea WormsShore BirdsMarine Food WebPhoto Source: The Lloyd Center at UMassDetritusGrazing Food WebMicrobial Food WebDetrivore Food WebNet Ecosystem Production= GPP - RA - ∑ RHDetrivoresDetrivoresRARHRHRHGPP11ststcarnivorecarnivore““RefractoryRefractory””CarbonCarbonRHRHHeatEtc.Etc.POCPOCDOCDOCPDAIDFFDetritusDetritusPOC= Part icu latePOC= Part icu lateOrg anicCarb o nOrg anicCarb o nDOC= Disso lvedDOC= Disso lvedOrg anicCarb onOrg anicCarb on2nd Carnivore2nd CarnivoreNPPMicroorganismsMicroorganismsIAPrimary producersPrimary producersherbivoresherbivoresGrasslandForestOpen OceanBiomass(grams/m2)Energy Flow(calories/m2/day)Pyramids of Biomass and EnergyProducers Herbivores CarnivoresInverted Pyramidof BiomassBiomass tied up inwood & unavailableto herbivoresBiomass in greenplants, accessible toherbivoresSee alsoSee alsoFig. 55.7Fig. 55.7in textin textPhotosynthetic Organisms(Our world depends on this for food and fiber)RespirationProcess:PhotosynthesisExcretion and DeathRespirationDigestion, assimilation, & growthAnother Representation of Energy FlowThrough an EcosystemDetritivoresHerbivoresPrimarycarnivoresSecondarycarnivoresThe majority of energyis lost to respirationand is unavailable toother organismsSee alsoSee alsoFig. 55.3 inFig. 55.3 intexttext4RespirationDirect Use(food, fuel,fiber, timber)Productive capacity lostby land conversion &desertification oroveruse(open land to cities, foreststo cropland etc.)Human Appropriation of PhotosynthesisDetritivoresHerbivoresPrimarycarnivoresSecondarycarnivoresDiverted Productivity(crop waste, lumberwaste, burning etc)Small%largest%Medium%Between 10 and 55% has been appropriated(difficult to estimate)Take Home MessagesTake Home MessagesMassive amounts of carbon flow through photosynthesisMassive amounts of carbon flow through photosynthesiseach yeareach yearMarine and Terrestrial ecosystems Marine and Terrestrial ecosystems roughlyroughly same amount same amountCarbon/energy flows through food websCarbon/energy flows through food webs80-90% dissipated with each 80-90% dissipated with each trophictrophic transfer transferIn mature ecosystems, nearly all that is produced is eatenIn mature ecosystems, nearly all that is produced is eatenHumans have co-opted a significant fraction of globalHumans have co-opted a significant fraction of globalprimary productivityprimary productivityBlue Planet DVDBlue Planet DVDThree weeks in the life of aThree weeks in the life of aMarine Food WebMarine Food WebThink About:Think About:••The massive amount of energy andThe massive amount of energy andcarbon the phytoplankton must becarbon the phytoplankton must beprocessing to support such a diversity andprocessing to support such a diversity andbiomass at higher biomass at higher trophictrophic levels levels••How the information in DNA could beHow the information in DNA could becontrolling all of these complex processescontrolling all of these complex
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