Ecosystem fluxes and cycles Ecosystem efficiency and trophic transfers Tipping points between blue water and green water states in lakes and rivers Ecosystem cycles of water carbon phosphorus and nitrogen Ecosystem ecology Energy flows and nutrients cycle through ecosystems Humans are increasingly changing Earth s biogeochemical cycles 1 2 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 O C N Ca P created in stars used again and again end up in different pools fluxes transfer atoms between pools We Are Stardust Science Daily June 25 1999 When Joni Mitchell in her song Woodstock sang We are stardust she was being factual as well as poetic Every element on earth except for the lightest was created in the heart of some massive star 3 4 Terrestrial bottom heavy pyramid of trophic level biomass Photosynthesis Inputs Outputs Change in storage 5 6 PN 1 Resource Production Not consumed ingested Ingested feces excreted assimilated EN IN Not consumed Dead organic matter P N 1 Assimilated used for maintenance respired used for production of new tissue or offspring PN 7 Food produced Allocations that compete with growth and reproduction defense stress Herbivore Yellow system has shorter turnover time than blue system Inverted pyramid of Trophic level Biomass Clean water and fish suppress output input I ingestion A assimilation F egestion R respiration P production 8 Turnover time if system is in equilibrium input vol time 1 output vol time 1 q Residence time T Volume q Turnover rate fraction of storage that is replaced in a given unit of time 1 T storage storage Microbivore Detritivore Food quality is an important factor affecting production efficiency Stocks pools compartments and flows fluxes Input Output Change in Storage 0 at equilibrium input Carnivore Invert consumer AN Efficiency of trophic transfer for secondary production Vert ectotherm RN P n P n 1 Vert endotherm Trophic level efficiency PN PN 1 often 10 PN sustain output 9 Or bottom heavy trophic pyramid dominated by Cyanobacteria in a eutrophied lake 10 Clear water state Stabilized by 11 nutrient sequestration in longlived top predators upslope vectoring of nutrients by scavengers and predators salmonids birds bats bears terrestrial vegetative cover frequent scour and flushing that maintain edible prey taxa Green water eutrophic state 12 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 13 Eutrophic state stabilized 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 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 N2 14 What are we doing to rivers Flow regulation diversion and extraction Water extracted fine sediments solutes and heat added 15 16 Bioaccumulation of DDT PCBs Hg and other toxins 17 SF Chronicle Nov 23 2003 Double edged swordfish top of their food chains and very long lived species 18 The California water system The most massive rearrangement of Nature ever attempted Kahrl et al 1978 River network fragmentation blue lines on maps haven t been connected on ground for 50 years Disturbance removal Habitat simplification fragmentation 19 Terminus of Cowchilla R should be a tributary of the San Joaquin but dies in an agricultural field Photos W E Rainey 20 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 erosive runoff 21 Permeability of the surface path that water takes from land to rivers determines time interval for storage and flashiness of floods 23 22 Evapotranspiration Evaporation and transpiration loss of water through stomates of plants 24 Plants changes in stomate behavior and roots will affect evapotranspiration and storage of water Organic compounds contain C and H CO NH2 C6H12O6 Carbon 2 Campbell p 1209 Inorganic CO2 NH4 NO325 Less evaporation less precipitation Available to biota Unavailable26 Carbon cycle Campbell p 1211 Unavailable until mined 27 28 Phosphorus cycle No gaseous atmospheric component 29 30 Nitrogen cycle more complex than P cycle Phosphorus Fig 27 3 Krebs P residence time algae days weeks animals days years soils months millenia ocean sediments millions of years The Nitrogen Cycle 31 32 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 33 bioavailable nitrogen Vitousek 1997 34 Vitousek 1997 Ecol Applicns Importance of forest 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 resolution35to the war stream p 1214 Campbell Tree cutting completed deforested Losses during floods control 36 Ecosystem efficiency organic production nutrient flux mass time t mass time t Stream Ecosystem efficiency organic production nutrient flux mass time t mass time t flow Stream spiraling Newbold Webster downstream transport with periodic cycling by local biology backflows 37 Retentive ecosystems with short spiral lengths are
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