Presentation on theme: "Individual organism: How do structure, physiology, and behavior lead to the individual’s survival and reproduction? Population: What determines the number."— Presentation transcript:
1 The hierarchical nature and processes of different levels of ecological systems:
2 Individual organism: How do structure, physiology, and behavior lead to the individual’s survival and reproduction?Population: What determines the number of individuals and their variation in time and space?Community: What determines the diversity and relative abundance of organisms living together?Ecosystem: How does energy flow and matter cycle in the biotic and abiotic environment?Biosphere: How do air, water, and the energy and chemicals they contain circulate globally?
3 Ecosystem Ecology: Interactions between abiotic and biotic factors at a given location as relates to: energy flow and cycling of matter.IB 452: Ecosystem Ecology fall 2011IB 440: Plants and Global Changespring 2011
4 Energy flow in ecosystem Objectives: Ecosystem obeys thermodynamic principles.Trophic pyramid for energyPrimary production: efficiencies andfactors causing variation among biomesSecondary production:Intertrophic transfers: efficiencies andfood chain lengthIntratrophic transfers: efficienciesNet ecosystem production: C gain - C loss
5 Food energy available to the human population depends on their trophic level. C Eating meat is inefficient way of tapping PS productivity. Humans obtain far more calories by eating grains directly as a primary consumer than by prcessing that same amount of grain through another trophic level. We could feed many more people if we all consumed only plant material, feeding more efficiently as primary consumers224 billion tons of plant production/year59% = terrestrial35-40% used by humans directly (as plants) or indirectly (by feed animals first)Food supplies can be increased and morepeople can be supported by eating lower onfood chainFigure 15
6 Ecosystem: an energy-transforming machine Exchanges of matter and energy among componentsObey thermodynamic principles that govern energy transformationsLaw 1: Conservation of energy“balance the books”Law 2: Inefficient transformation of energy“heat tax”Law 1: energy neither created nor destroyed: have to ‘balance the books’
7 ‘Universal’ model of energy flow through ecosystems.
8 Coupling of oxidations and reductions = basis of energy flow in ecosystems.
9 Energy flows through biochemical pathways Energy flows through biochemical pathways. Energy transfer decreases after each transformation.
10 Heat is lost as energy flows through food chain. Matter recycles… Blue = matterRed = energyWhat do red and blue arrows =? Blue = matter; red = energy
11 Primary Production: by plants process of converting light energy to chemical bond energy in carbohydrates(via photosynthesis!)for each g of C assimilated, 39 KJ energy storedrate determines rate of energy supply to rest of ecosystem
12 GrossPP = NetPP + Respiration Day + nightDayFigure 2
13 IRGA - Infrared gas analzyer: measure CO2 in vs IRGA - Infrared gas analzyer: measure CO2 in vs. out: in sunlight (NPP) and dark (respiration); estimate GPPB15.14
15 How measure assimilation and respiration of CO2 over large spatial scales? Use eddy flux covariance towersSensors quantify vertical movement of CO2 in atmosphere above vegetation.How temp and precip control primary proudction affect respiration of plantsHelps to predict how ecosystem productivity migh change in response to climate change.
16 Abiotic Limits on Productivity Photosynthetic efficiency(% energy from sun converted to NPP)= 1-2%Net production efficiency (NPP/GPP)30% tropics % temperate***why difference?Variables affecting productivity:LightTemperaturePrecipitationNutrientsCO2
18 NPP vs. Temperature and Precipitation Effects of TemperatureOptimum varies from 16 to 38Rate of PS increases with T, but so does respirationNet assimilation may decrease at high temperaturesEffects of WaterPS on land is water-limitedWater-use efficiency: 2 g production per kg of water transpiredWater use efficiency =G NPP per kg water transpiredFigure 5
19 NPP vs. nitrogen (N in rubisco in PS) Nutrients stimulate primary productionN = most common limiting element; then P on landAquatic systems often nutrient-limitedNutrient use efficiency =g production per g N assimilatedFigure 6
20 NPP + > [CO2] To what extent is PS limited by amount of CO2? To what extent does vegetationact as a C sink?
21 Remote sensing of primary production in oceans. Spectral instrument estimates chlorophyll conc and converts data to contrasting artificial colors.
22 1° productivity of aquatic ecosystems depends on [nutrients]. Freshwater lakes:P often limiting;with low N/P, blue-green algae increase NPPbecause they can fix additional N;with high N/P, green algal ‘blooms’ occurOpen ocean:near shore: N often limitingopen ocean: silica and Fe more limiting
23 PP in aquatic ecosystems - highest where nutrients regenerated in sediments reach light zone. Figure 7
24 Question: Is NPP in the open ocean limited by nutrients (e.g Fe)? Hypothesis: NPP in the open ocean is limitedby availability of iron.Experimental setup?Prediction: Amount of chlorophyll a increases both at surface and 30 m deep in area with added Fe relative to area without Fe.
25 Southern Ocean Iron Enrichment Experiment Southern Office Iron Enrichment Experiment (SO FEX) in areas of high and low silicon concentrations25
27 Results: satellite images White = cloudFalse-color satellite images of each experimental area showing greatly increased phytoplankotn proudciton (as indiciate by chlorophylll a reflectance.27
28 What is the conclusion? Figure 8 Fe fertilization increases ocean as C sink…but it also stimulates zooplankton production which releases CO2 to atmosphere and counters C sink argument.The So FE exp were more promising as much C precipitated below water mixing zoneWhat is the conclusion?Figure 8
32 Energy flows through:Food chain – energy passes through many steps or linksTrophic level (feeding level) = each link in food chainTwo parallel food chainsPlant-basedDecomposer-based32
33 Food chains represent energy relationships. Consumers(heterotrophs)Ecosystem trophic structure model: Spatial pattern set by autotrophsDecomposers blur the patternPredators link components, stabilize systemProducers (autotrophs)33
34 Energy Pyramid: 10% law of energy transfer; 2nd law limits number of levels. 90% lost at each level.1110100Figure 10
35 Energy transfer between trophic levels depends on: NPPefficiencies of transfer between trophic levelsresidence timelonger time--> > accumulation of energyMonitor energy fluxes by considering various efficiencies and residence times of energy and results from food chain processing of energy by animals.Residence time varies: short in aquatic zooplankton; long in landLonger residence time - greater time to accumulate energy (biomass)
36 Ecological (food chain) efficiency = net production of trophic level_n net production of trophic level n-11015201sunFigure 11
37 Ecological (food chain ) efficiency Production of each trophic level =5 – 20% that of level below itReplaces the “10% law”= an average; not fixedOften lower on land (5-15%) than aquatic (15-20%)
39 What limits length of food chain? H1: EnergeticsAvailability of energy limits to 5-7 levelsDepends on:NPPenergy needed by consumersaverage ecological efficiencyH2: Dynamic stabilityLonger chains less stable because:Fluctuations at lower trophic levels magnified athigher levels --->extinction of top predators.Microcosms - useful for such tests…replicate essential features of ecosystem. Control all variables except ones of interestGet pix of 1.20
40 Do aquatic or terrestrial ecosystems have more trophic levels ***Do aquatic or terrestrial ecosystems have more trophic levels? What factor contributes most to variation in food chain length among these ecosystems? Community NPP Consumer Ecological # Trophic Ingestion Efficiency% Levels Open ocean Coastal marine Grassland Tropical forestFigure 12
41 Secondary production By non-photosynthesizers Amount of chemical energy in consumer’s food converted to biomass /unit timeSecondary production
42 Energy flow within a trophic level Secondary production = assimilated energy – respiration – excretionFigure 13
43 Some general rulesAssimilation efficiency increases at higher trophic levels.Net and gross production efficiencies decrease at higher trophic level.Ecological efficiency averages about 10%.About 1% of NPP ends up as production on third trophic level;The pyramid of energy narrows quickly.
44 Net Ecosystem Production (NEP) = carbon gain - carbon lost Measures net carbon accumulation -->carbon ‘sequestered’ in organic cmpds insoil and living biomass -->no ‘greenhouse’ warming effectPositive NEP represents carbon sink -->removes CO2 from atmosphere
45 Exam ? Energy (kcal m-2 yr-1) Energy production Primary Primary Secondary__or removal_____ Producers Consumers ConsumersNon-consumed productionRemoved by consumersRespirationGross production (totals) ____ ____ ____1) Calculate NPP _____2) Calculate Ecological Efficiency during 2 transfers(= food chain efficiency) ______ ______3) What ultimately happens to 1) the energy and 2) thebiomass that is not consumed in this lake?N.B. NPP - non-consumer+ consumedEcological Efficiency = net 2ndP/net P so 104/880=11.8% and 13/104=12.5%