Introduction to Ecosystem Theory

Toward an EcosystemTheory –• By Sven Erik Jørgensen, DFU,Institute A, Environmental Chemistry,University Park2, 2100 CopenhagenØ, Denmark.• sej@dfuni.dkdk

Outlines:• 1)Presentation of the basic laws in antentative ecosystem theory• 2) Presentation of an Ecological Law ofThermodynamics denoted ELT byintroduction of eco-exergy• 3) Application of the theory to a) explainecological observations or rules b) todevelop structurally dynamic models• 4) The theory is consistent with otherapproaches: we have an ecosystemtheory• 5) Conclusions: let use this ecosystemtheory more widely

A WORLD EQUATION ????THE BASIC LAWSNEWTON’SMAXWELL’S EINSTEIN’SSLAWSLAW OF E-RELATIVITYLECTRICITY THEORIESQUANTUMTHEORYTHERMODYNA-MIC LAWSLAWS OFRADIATIONA number of laws, cove-ring many physical relationshipsALL POSSIBLE OBSERVATIONS

1. Ecological Law:• Mass and energy conservations arevalid for ecosystem.• This law is used widely in ecologicalmodelling, population dynamics, bythe allometric principles and in theexplanation of numerous ecologicalobservations

2. Ecological Law:• All processes in ecosystems areirreversible and are accompanied byentropy production and exergydestruction.• This law gives an understanding of theenergy utilization in ecosystems, heatproduction by respiration and all energybalances for ecosystems or organisms• Irreversibility (time arrow) is a prerequisitefor the ecosystem development, theevolution and the history (Prigogine).

3. Ecological Law• All ecosystems are open systemembedded in their environment. Theyreceive energy - matter anddischarge energy (heat) -matteroutput• This law explains that ecosystemscan stay far away fromthermodynamic equilibrium in spiteof the second law. Ecosystems mustbe open to respect the 2. Ecological

Openness can be quantifiedas:Periphery / area or surfacearea / volume• The openness determines howvulnerable the system is• The openness determines how fastan ecosystem can recovered afterdestruction• The openness determine the relativeemigration and immigration rate

Disturbances: scale and recoveryVitousek, P.M. 1994. Ecology 75: 1861-1876.

4. Ecological Law• Ecosystems operate and are organizedhierarchically• The properties of a population aredetermined by the properties of theindividuals and the population isinfluencing the properties of theindividuals• The law is widely used to understand theproperties p of a focal level in theecological hierarchy

The organism: a result of the sumof the functionsof the organsOrgan level:specific function forthe organismThe life conditionof the organismdetermine the functionability of theorgansCell level:small biochemicalfactoriesThe organ controls thebiochemistry of the cellsMolecular level:biochemistryThe cell controls thebiochemical i processes

5. Ecological Law• The components in an ecosystemform a complex interactive, selforganizingg ecological network• This law is widely used to explainecosystem reactions. It is thereforealso used to overview ecosystemreactions in form of conceptualdiagrams, that are the basis fordevelopment of ecological models

This law has been used widely byPatten et al. To understand theproperties of ecological networks• Indirect effects are often≥directeffects• The input-output t t relationships• Energy and information, not onlymass recycle• The network can explain synergisticeffects; compare with the Gayahypothesis• Ecosystems have history that isdecisive for the reactions and

6. Ecological Law• Ecosystems and their components(the organisms) have a characteristictibiochemistry, that is able to explainthe elementary ratio of organismsand ecosystems (≈ 25 elements), thatvaries surprisingly i little fromecosystem to ecosystem and fromorganism to organism.• Redfield ratio: C:N:P = 48:7:1.• Explanation of stoichiometry ofecological reactions

7. Ecological Law• Carbon based life requires 250-350 K, where there is a balancebetween ordering anddisordering processes• Notice at 0K: no disorder and noordering processes

8. Ecological Law:• Ecosystems have a complexdynamics. They can grow anddevelop by three growth forms:• Growth of biomass (the physicalstructure of the organisms) I• Growth of the network II• Growth of information III

What is exergy?• Exergy is work capacity - energy that cando work. It can therefore be found as thegradient (= difference in potential)xextensive descriptor , dependent d on theenergy form, for instance• Chemical energy= (µ 1 -µ 2 ) N or• Pressure energy= (p 1 -p 2 )(-V))• Potential energy= (h 1 -h 2 ) m g• Electrical energy= (V 1 - V 2 )Q

We may distinguishbetween technologicalexergy and eco-exergy:• Technological l exergy uses theenvironment as reference state andis useful to find the first class energy(work) that a power plant canproduce• Eco-exergy uses as reference statethe same ecosystem with the sametemperature e and pressure e but atthermodynamic - chemicalequilibrium

System at T, pDisplacement work,not usefulWork (exergy)Reference environmentat T, p

How to find the eco-exergy?• i=n i=n• Ex = ∑(µ 1 - µ 2 ) C i = RT ∑ C i ln C i / C i,o• i=0 i=0• n• A=∑c i p i =c i /A• i=1•n•Ex = A RT ∑pi ln pi / pio + A ln A /Ao = ARTK,i=1• where K is Kullbach’s measure of information

Free Energy and Eco-exergy• Eco-exergy seems to be just a difference infree energy, but it is not the case, because• 1) The reference state is different from caseto case• 2) Eco-exergy is not a state function. Noticethe difference in eco-exergy between a livingand ddead dorganism is the enormouscontribution from information. Eco-exergy cantherefore not be differentiated.• 3) Eco-exergy is the biomass (containing freeenergy) times the information.

9. Ecological Law (ELT I):• A system that receives a through-flow ofexergy (free energy) (for instance solarradiation for an ecosystem) will utilize theexergy (free energy) to move away fromthermodynamic equilibrium = gain exergy• We know that the ecosystem reactions todevelopment are in accordance with E.POdum’s attributes, that are in accordancecewith growth forms I, II and III and we knowthat all three growth forms implyincreased exergy, so the 9. Ecological Lawmust be valid

10. Ecological Law: (ELT II)• If the ecosystem is offered morepathways or combinations ofpathways to move away fromthermodynamic equilibrium, then thecombinations of pathways that movethe system most away fromthermodynamic equilibrium / yieldthe highest eco-exergy of theecosystem, will win.• A thermodynamic translation ofDarwin ≈ survival of the fittest can beexpressed as ART K where A is the

Stability concepts have to bequantitative to be useful (R.Margalef)• Buffer capacity (or resistance capacity) =Δ forcing function (impact) / Δ state variable.Notice it is a multidimensional concept (manycombinations of forcing functions and statetvariables).• Eco-exergy for models is proportional to thesum of many buffer capacities• High biodiversity implies an increasedprobability for a wider spectrum of buffercapacities

Reaction kJ/mole e-ATP's/mole e-________________________________________________________CH2O + O2 >CO2+H2O125 298 2.98CH2O + 0.8 NO3– + 0.8 H+ CO2 + 0.4 N2 + 1.4 H2O119 2.83CH2O + 2 MnO2 + H+ CO2 + 2 Mn 2+ + 3 H2O85 2.02CH2O + 4 FeOOH + 8 H+ CO2 + 7 H2O + Fe2+27 0.64CH2O + 0.5 SO42– + 0.5 H+ CO2 + 0.5 HS– + H2O26 0.62CH2O + 0.5 CO2 CO2 + 0.5 CH423 0.55_________________________________________________________

What is the eco-exergy exergy ofhigh molecular organics?•-∆G =RTlnK.• –∆G = - 18.7 kJ/g *104400g/mole = 1952 MJ / mole = 8.2J /mole *300 lnK,• which implies that lnK = -793496 or K is about 10 -344998

How to find the eco-exergyexergycontent of living organism?• Eco-exergy = ∑ßI*ci,• Where ß is a weighting factor = RT lnci/cio, considering what the probability isto form the organism at thermodynamicequilibrium, ie. How many amino acidsin the right sequence is required tomake up the organism, i.e how muchinformation does an organism contain?

ß-values found from thegenome sizes I• Organisms Genome Mb Repeat % ß• Human 2900 46 2149• Mouse 2500 38 2127• Tiger fish 400 9 499• Mosquito 280 16 322• Squirt 155 10 191• Fruit fly 137 2 184• Yeast 12 2 16• Amoeba 34 0.5 46

ß-values found from thegenome sizes I• Organisms Genome Mb Repeat % ß• Human 2900 46 2155• Mouse 2500 38 2127• Worm 97 0.5 153• Mustard weed 128 14 147• Rice 400 50 275• Virus 1.01• Reptiles 833*)• Birds 980*)• *) found indirectly

Circulation rates ofnutrients as function ofrelative concentrations ofRnutrients?2.5 +2.0++1.0 +++0.50.5 1.0 1.5 2.0Log (N / P)

Structurally dynamicmodels:• Are able to account foradaptation and shift in speciescomposition• The model can assist us in theunderstanding of observedstructural changes• The model can explain when itwill be a success and when it bea failure to applybiomanipulation

External factorsForcingfunctionsNew recombinationsof genes /mutationsEcosystem stemstructure at time tGene poolSelectionEcosystemstructure at timet+1

Galilei: measure everythingand what is not measurablemake measurable

Galilei modified: modeleverything and, what is notmodelable make modelable

PREVAILING CONDITION 1STRUCTURE 1The structure is changed, because theprevailing conditions are changed - andadaptation and/or shifts in species com-position can give a better survival inthe Darwinian sense. Survival is measuredas biomass and information -therefore exergy can be applied as goalfunctionPREVAILING CONDITION 2EXERGY ISUSED ASGOAL FUNC-TION TO DE-TERMINE THESTRUCTURALCHANGESSTRUCTURE 2

Select parameters based upon literaturestudies and according to speciescompositionSelect most crucial parameters, symbolizedby parameter vector PTest after time step t all combinations ofall the selected parameters +/- x%, y% etci.e. at least three leves for each parameter.The total number of combinations to be e-xamined is l n, where l is the number of levelsand n is the number of parameters inthe parameter vector P. The combinationgiving the highest exergy is used for thesimulation during the considered time stepTest after time step n*t all combinations ofTest after time step n t all combinations ofthe selected parameters +/- x%, y% etc.The combination giving the highest exergyis used for the simulation duringe the consideredtime step

Eutrophication, (measured by phytoprimary production)plankton conc. orRange, wherebiomanipulationnot isappliedRange, where biomanipulationcan be appliedFaster recoveryobtain-ed by bio-maipulationRange, wherebiomanipulationhardly can beappliedNutrient concentration

Two structures arecompeting:• Below 60 µg P/l zooplankton andcarnivorous fish dominanceAbove 125µg P/l phytoplankton andplanktivorous fishBetween 60 and 125µg P/l bothstructures are possible dependenton the history

Shallow lakes have twocompeting structures, too:• Below about100 µg P /l submergedvegetation is dominant• Above about 250µg P/l phytoplanktonis dominant• Between about 100 and 250 µg P/l thetwo structures are both possible,dependent on the history

Results obtained by astructurally dynamic model:1412P_SP (g/m^ ^2)10864200 0.1 0.2 0.3 0.4 0.5 0.6TP (m g P/l )

We have three growth forms•1) Biomass - physicalyscastructure• 2) The network• 3) The informationNotice that they summarizethe E.P. Odum’s attributest

Growthforms2and3arearedifferent from growth form 1:• They are not following theconservation principlesi • An ecological network has morepositive than negative relations• Information can be copied at almostno cost• The two growth forms are far fromtheir limits

It has been examined by useof models and ecologicalknowledge / E.P. Odums,• How the exergy, specific exergy= exergy / biomass, exergydestruction (The Extended 2.Law), power,, entropyproduction, change with thegrowth forms I, II and III.

Growth AB C D ESpec. entropy Power Exergy de- Exergy sto- RetentionProduction struction rage time_________________________________________________________________________I unchanged(-) increases(+) increases(+) increases(+)increases(+)II decreases(+) increases(+) unchanged(-) increases(+)increases(+)III decreases(+) increases(+) unchanged(-) increases(+)increases(+)_________________________________________________________________________

100806040*** * * *200*0 20 40 60Exergy (MJ / m 2 )

umbers180 ..RegenerationJuvenileOptimum. .MixedExergy de estruction,relative n160140. Gap. Pasture120 0 5 10 15 20 25 30 35 40Exergy stored (GJ / ha)

Recently at a brainstorming meetingon the Danish Island Møn, it waspossible to “hang” these 10 laws on 5ecosystem properties:

Recently at a brainstorming meetingon the Danish Island Møn, it waspossible to “hang” these 10 laws on 5ecosystem properties:

Recently at a brainstorming meetingon the Danish Island Møn, it waspossible to “hang” these 10 laws on 5ecosystem properties:1. Ecosystems have directionality2. Ecosystems are open systems3. Ecosystems have connectivity4. Ecosystems have emergenthierarchies5. Ecosystems have complexdynamics

We do have an ecosystem theory!Why do we not apply this theorymore widely in ecology andenvironmental sciences?• It should be applied toexplain ecologicalobservations and used astool in ecologicalengineering!!

Ecosystem Theory books:• S.E. Jørgensen. Integration ofEcosystem Theories: A Pattern,Kluwer, Third edition, 2002.• S.E.Jørgensen and Y.SvirezhevToward a Thermodynamic Theory forEcological Systems. Elsevier. 2004.

CONCLUSIONS• We do have an ecosystem theory-orrather a pattern of ecosystemtheories. It is still underdevelopment, but is sufficientlydeveloped to day to be applied,as it has been shown.We ought to apply it more widelyWe ought to apply it more widelyin ecology

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