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Berkeley BIOLOGY 1B - Ecosystem fluxes and cycles

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1Ecosystem fluxes and cycles• Carbon, P, and N cycles• Ecosystem “efficiency”• Toxins and bioaccumulation• Water management• Translocations of nutrients byorganisms2Ecosystem ecology• Energy flowsand nutrientscyclethroughecosystems• Humansincreasinglyare changingbiogeochemical cycles andspatialdistributionsof storage3Stocks (pools, compartments) and flows (fluxes)Input - Output = Change in Storage (= 0 atequilibrium)Turnover time: if system is in equilibrium,input (vol time-1) = output (vol time-1) = qResidence time, T = Volume/qTurnover rate (fraction of storage that is replacedin a given unit of time) = 1/Tstorageinput outputstorageinput outputYellow system hasshorter turnover timethan blue system.4Materials cycle—atoms (O, C, N, Ca, P ) created in stars, used again andagain, end up in different pools, fluxes transfer atoms between pools.Energy flows—a small fraction of solar radiation is fixed byphotosynthetic organisms, but once energy is dissipated as heat, it is neverrecovered by ecosystem (except as passive energy savings fortransport—e.g. ocean or air currents driven by heat and used byorganisms)."We Are Stardust..."ScienceDaily (June 25, 1999) — When Joni Mitchell, in her song"Woodstock," sang, "We are stardust..." she was being factualas well as poetic. Every element on earth, except for the lightest,was created in the heart of some massive star.567PhotosynthesisInputsChange in storageOutputs8Terrestrial (bottom-heavy) pyramid of trophic level biomass9Trophic level (N)efficiency (often 10%)Resource Production N-1 =Not consumed + ingestedIngested = feces excreted+ assimilatedAssimilated = used formaintenance (respired)+ used for production (newtissue or offspring = PN)P N-1PNNotconsumedDeadorganicmatterANINENRNFood producedconsumerBegon et al. 199710 Herbivore Carnivore Microbivore DetritivoreVert endotherm Vert ectotherm InvertI = ingestionA = assimilationF = egestionR = respirationP = productionEfficiency oftrophictransfer forsecondaryproductionAllocationsthatcompetewith growthandreproduction(defense,stress)P n / ( P n-1)Food quality is an important factor affecting production efficiency11Inverted pyramids of trophic level biomassClean water, and fish—Two ecosystem services brought to you by:suppresssustain12Eutrophied lake, Queensland, Australia13Most serious consequence of greenhouse warmingwill be the redistribution of water in space andtime:reduced snowpack storage in Sierraincreased intensity of stormsflashy runoffHydrologic cycle:Evaporation = PrecipitationTransfer processes:atmospheric transport,runoff14Hydrologic (water) cycle15Permeability of the surface: path that water takesfrom land to rivers determines time interval forstorage, and “flashiness” of floods(land use effects, e.g. Philippines)16Affected areashave lost 20% offorest coverover the last 10years.Infiltration ofrain reduced, soflows flashy,erosive. Rootsdecay over time,triggering mudslides. 4 peoplekilled by this inCoos Bay Oregon1997.17Evapotranspiration: Evaporation andtranspiration (loss of water through stomates ofplants)18Plants: changes in stomate behavior and roots willaffect evapotranspiration and storage of waterLess evaporation ! less precipitation19Campbell,p. 1209CO2NH4+NO3-CO (NH2) 2C6H12O6(Organic compoundscontain C and H)Available to biotaUnavailableInorganicNutrients (N,P) and carbon20Carbon cycle (Campbell p. 1211)21Unavailableuntil mined2223Campbell,p. 1209CO2NH4+NO3-CO (NH2) 2C6H12O6(Organic compoundscontain C and H)Available to biotaUnavailableInorganicNutrients (N,P) and carbon24Phosphorus cycle: No gaseous, atmospheric component25Fig. 27.3,KrebsP residence time:algae: days-weeksanimals: days-yearssoils: months-milleniaocean sediments: millions of yearsPhosphorus26Nitrogen cycle: more complex than P cycle27http://www.physicalgeography.net/fundamentals/9s.htmlHuman activities (fossil fuel combustion, syntheticfertilizers, cultivation of legumes, industrial meat production)have more than doubled the natural input rate of fixed(bioavailable) nitrogen (Vitousek 1997).The Nitrogen Cycle2829V. Smil 1997. Scientific American. Curiousfate of Franz Haber* German chemist,awarded Nobel Prize 1919 for ammoniasynthesis. Haber-Bosch synthesis of ammoniafrom nitrogen and hydrogen, combined at hightemps and pressures! explosives for WWIbut world fertilizers soon thereafter, allowinghuman population to exceed 6 billion….*also developedweaponizedchlorine gasused in WWI,hoping to limitoverallsuffering bybringing abouta quickerresolution tothe war.30Importance of land cover in retaining N high in the landscape—Hubbard Brook ExperimentGeneLikensp. 1214 CampbellTreecuttingcompletedcontroldeforestedstreamLosses during floods31Ecosystem efficiency:organic production/nutrient flux(mass time-t / mass time-t )Forests more efficient at producing wood fromnutrients if these are retained.32Terrestrial nutrient and soilretention degraded by wind erosion indesert after loss of desert crustsATVtracksCrust vsDust:Desertcryptogams33Stream Ecosystem efficiency:organic production/nutrientflux(mass time-t / mass time-t )Stream spiraling (Newbold,Webster): downstreamtransport with periodic cyclingby local biologybackflowsflow34Retentive ecosystems with shortspiral lengths are more efficient-- more biotic production pernutrient flux downstream.They also protect downstreamwater bodies from eutrophicationBiologicalbackflowsWetlands, logs in rivers, biologicalbackflows (e.g. salmon migrations)increase retention, ecosystemefficiency, and decrease spiral length.35Waterextracted,fine sediments,solutes,and heat added.What are we doing torivers?Flow regulation,diversion andextraction36Bioaccumulation of DDT, PCBs, Hg, and other toxinsCampbell37SF Chronicle Nov. 23 2003Double-edged swordfish:top of their food chains,and very long lived species38The Californiawater system:“The most massiverearrangement ofNature everattempted”(Kahrl et al.1978)Disturbance removal;Habitat simplification fragmentation 39River networkfragmentation:blue lines onmaps haven’tbeenconnected onground for 50yearsTerminus of Cowchilla R.should be a tributary ofthe San Joaquin, butdies in an agriculturalfield.Photos, W.E. Rainey40Clean water, and fish—suppresssustain41Or “bottom heavy” trophic pyramid dominated by Cyanobacteria in a eutrophied lake?42Or “bottom heavy” trophic pyramid dominated by Cyanobacteria in a eutrophied lake?43stabilized or maintained by:


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Berkeley BIOLOGY 1B - Ecosystem fluxes and cycles

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