1Ecosystem fluxes and cycles• Carbon, P, and N cycles• Ecosystem “efficiency”• Toxins and bioaccumulation• Water management issues• Translocations of nutrients byorganisms2Ecosystem ecology• Energy flowsand nutrientscyclethroughecosystems• Humansincreasinglyare changingbiogeochemical cycles andspatialdistributionsof storage3Materials cycle—atoms (H, O, C, N, Ca, P ) created in stars, used again andagain, 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/qstorageinput outputEnergy 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).storageinput outputYellow system hasshorter turnover timethan blue system.4Terrestrial (bottom-heavy) pyramid of trophic level biomass5Freshwater and Marine:Inverted pyramids of trophic level biomasssuppresssustain6Eutrophied lake, Queensland, Australia7 “Bottom heavy” trophic pyramid dominated by Cyanobacteria8stabilized 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; *frequent scour and flushing thatmaintain edible prey taxaClear water state:Green water,eutrophic state:9Switch from oligotrophic to eutrophic state: Land conversion -loss of wetlands, forests -erosion, fine sediment loading -sewage, agrochemicals Water management (extraction, impoundment, diversion): -loss of flushing flows, habitatN210Eutrophic state stabilized, maintained by: *internal nutrient cycling enhanced by hypoxia; *loss of higher trophic levels due to hypoxia and inedible algae *more bank erosion with loss of rooted terrestrial vegetation; *nitrogen fixation by cyanobacteria that dominate under high P N211Most 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,runoff12Hydrologic (water) cycle13Permeability of the surface: path that water takesfrom land to rivers determines time interval forstorage, and “flashiness” of floods(land use effects, e.g. Philippines)14Affected 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 Oregon1997.15Evapotranspiration: Evaporation andtranspiration -- loss of water through stomatesof plants during Photosynthesis:6 CO2 + 12 H2O !"C6H12O6 + 6 O2 + 6 H2O16Plants: changes in stomate behavior and roots willaffect evapotranspiration and storage of waterLess evapotranspiration ! less precipitation17Campbell,p. 1209CO2NH4+NO3-CO (NH2) 2C6H12O6(Organic compoundscontain C and H)Available to biotaUnavailableInorganicMaterial Cycling18Carbon cycle (Campbell p. 1211)19Unavailableuntil mined20Phosphorus cycle, Cambell p. 1212. No gaseous, atmosphericcomponent21P residence time:algae: days-weeksanimals: days-yearssoils: months-milleniaocean sediments: millions of yearsPhosphorus22Nitrogen cycle, Campbell p. 1211—more complex than P23http://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 Cycle2425V. 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.26Importance of land cover in retaining N high in the landscape—Hubbard Brook ExperimentGeneLikensp. 1214 CampbellTreecuttingcompletedcontroldeforestedstreamLosses during floods27Terrestrial nutrient and soilretention degraded by wind erosion indesert after loss of desert crustsATVtrackscryptogams28Ecosystem efficiency:organic production/nutrient flux(mass time-t / mass time-t )Forests more efficient at producing woodfrom nutrients if these are retained.Oligotrophic lakes produce more fish pernutrient flux than eutrophic lakes29Stream spiraling: downstreamtransport with periodic cycling bylocal biology.Retentive ecosystems with shortspiral lengths are more efficient-- more biotic production pernutrient flux downstream.BiologicalbackflowsWetlands, logs in rivers, biologicalbackflows (e.g. salmon migrations)increase retention, ecosystemefficiency, and decrease spiral length.30The Californiawater system:“The most massiverearrangement ofNature everattempted”(Kahrl et al.1978)Disturbance removal;Habitat simplification fragmentation31River networkfragmentation:blue lines onmaps haven’tbeen onnectedon ground for30 yearsTerminus of Cowchilla R.should be a tributary ofthe San Joaquin, butdies in an agriculturalfield.Photos, W.E. Rainey32Why should we care?Watershed healthpublic health--impactson downstream waterbodies and nearshoremarine waters33Coastal Zone Color ScannerNimbus-7 satellitePfiesteria piscicida, N.C.SewageandvolatilizedNH3 fromindustrialpig farmsBurkholder andGlasgow 1997Dinoflagellate34Ecosystem “healthier” with longer foodaquatic chains, if predators native.• Zero trophic levels: “drinkingtheir own automobile exhaust”• One trophic levels: nutrientassimilation and retention, buteutrophication• Two trophic levels:vegetation grazed down, butpestiferous insect emergence• Three trophic levels: smallfish• Four trophic levels: biggerfish• Five trophic levels: really bigfish, anglers, and
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