Ecosystem fluxes and cycles Carbon P and N cycles Ecosystem efficiency Toxins and bioaccumulation Water management issues Translocations of nutrients by organisms 1 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 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 Ecosystem ecology Energy flows and nutrients cycle through ecosystems Humans increasingly are changing biogeochemic al cycles and spatial distributions of storage 2 Terrestrial bottom heavy pyramid of trophic level biomass 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 input storage Yellow system has shorter turnover time than blue system output input storage output 3 Freshwater and Marine Inverted pyramids of trophic level biomass suppress 4 Eutrophied lake Queensland Australia sustain 5 6 Bottom heavy trophic pyramid dominated by Cyanobacteria Clear water state stabilized or maintained by 7 Green water eutrophic state nutrient sequestration in longlived top predators upslope vectoring of nutrients by mobile scavengers and predators salmonids birds bats bears terrestrial vegetative cover frequent scour and flushing that maintain edible prey taxa 8 Switch 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 habitat N2 9 Eutrophic 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 N2 10 Hydrologic water cycle Hydrologic cycle Evaporation Precipitation Transfer processes atmospheric transport runoff Most serious consequence of greenhouse warming will be the redistribution of water in space and time reduced snowpack storage in Sierra increased intensity of storms flashy runoff 11 12 Permeability of the surface path that water takes from land to rivers determines time interval for storage and flashiness of floods Affected areas have lost 20 of forest cover over the last 10 years Infiltration of rain reduced so flows flashy erosive Roots decay over time triggering mud slides 4 people killed by this in Coos Bay Oregon 14 1997 13 land use effects e g Philippines Plants changes in stomate behavior and roots will affect evapotranspiration and storage of water Evapotranspiration Evaporation and transpiration loss of water through stomates of plants during Photosynthesis 6 CO2 12 H2O C6H12O6 6 O2 6 H2O 15 Organic compounds contain C and H CO NH2 C6H12O6 Material Cycling 16 Less evapotranspiration less precipitation Carbon cycle Campbell p 1211 2 Campbell p 1209 Inorganic CO2 NH4 NO3 Available to biota Unavailable17 18 Phosphorus cycle Cambell p 1212 No gaseous atmospheric component Unavailable until mined 19 Nitrogen cycle Campbell p 1211 more complex than P Phosphorus P residence time algae days weeks animals days years soils months millenia ocean sediments millions of years The Nitrogen Cycle 20 21 22 http www physicalgeography net fundamentals 9s html Human activities fossil fuel combustion synthetic fertilizers cultivation of legumes industrial meat production have more than doubled the natural input rate of fixed 23 bioavailable nitrogen Vitousek 1997 24 Importance of land cover in retaining N high in the landscape Hubbard Brook Experiment V Smil 1997 Scientific American Curious fate of Franz Haber German chemist awarded Nobel Prize 1919 for ammonia synthesis Haber Bosch synthesis of ammonia from nitrogen and hydrogen combined at high temps and pressures explosives for WWI but world fertilizers soon thereafter allowing human population to exceed 6 billion Gene Likens also developed weaponized chlorine gas used in WWI hoping to limit overall suffering by bringing about a quicker resolution25to the war stream p 1214 Campbell Tree cutting completed deforested Losses during floods control 26 cryptogams Ecosystem efficiency ATV tracks Terrestrial nutrient and soil retention degraded by wind erosion in desert after loss of desert crusts 27 Stream spiraling downstream transport with periodic cycling by local biology Retentive ecosystems with short spiral lengths are more efficient more biotic production per nutrient flux downstream organic production nutrient flux mass time t mass time t Forests more efficient at producing wood from nutrients if these are retained Oligotrophic lakes produce more fish per 28 nutrient flux than eutrophic lakes The California water system The most massive rearrangement of Nature ever attempted Kahrl et al 1978 Wetlands logs in rivers biological backflows e g salmon migrations increase retention ecosystem efficiency and decrease spiral length Biological backflows 29 Disturbance removal Habitat simplification fragmentation 30 River network fragmentation blue lines on maps haven t been onnected on ground for 30 years Why should we care Watershed health public health impacts on downstream water bodies and nearshore marine waters Terminus of Cowchilla R should be a tributary of the San Joaquin but dies in an agricultural field Photos W E Rainey 31 Coastal Zone Color Scanner Nimbus 7 satellite Pfiesteria piscicida N C Sewage and volatilized NH3 from industrial pig farms Dinoflagellate Burkholder and Glasgow 1997 33 32 Ecosystem healthier with longer food aquatic chains if predators native Zero trophic levels drinking their own automobile exhaust One trophic levels nutrient assimilation and retention but eutrophication Two trophic levels vegetation grazed down but pestiferous insect emergence Three trophic levels small fish Four trophic levels bigger fish Five trophic levels really big fish anglers and wildlife 34
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