Ecosystem Energy and Nutrient Flow

Ecosystems 1. Biotic community and the abiotic environment. 2. Functional system which transfers and circulates energy and matter.

Function, not Species -- Stuff, not Things

Ecosystem: “a spatially explicit unit of the Earth that includes all of the organisms, along with all the components of the abiotic environment within its boundaries.” Gene Likens

ECOSYSTEM ECOLOGY ENERGY

Ecosystems Are Energy Transformers J.M. Teal (1962)

Trophic Structure Reminder Express trophic structure as energy transfer Energy pyramids can never be inverted Is there room for anyone else at the top of this food chain?

21.1 Production Energy flow in an ecosystem: primarily plants GPP: Gross Primary Production Energy fixed in photosynthesis NPP: Net Primary Production Biomass accrued by plants: wt. living plant material Energy loss: respiration, tissue turnover, herbivory

Characteristics of Top Carnivores not dense (few per unit area) because of ecological efficiency large territory (widely ranging) large body long life fast moving charismatic hunt-able Extirpation Indirect Effects – Trophic Cascade

Transfer Efficiencies Kcal m-2 y-1 P=1 I=10 R=2 AE=80% Carnivores A=8 E=7 P=10 R=50 I1=100 AE=50% Herbivores A=50 E=40 NPP=1000 R+E=1000 Plants A (GPP)=2000 AE= % Solar Energy= 1,000,000

Transfer Efficiencies Kcal m-2 y-1 P=1 I=10 R=2 AE=80% Carnivores A=8 E=7 P=10 R=50 AE=50% Herbivores A=50 E=40 I1=100 NPP=1000 R+E=1000 Plants A (GPP)=2000 AE= % Solar Energy= 1,000,000

Transfer Efficiencies Kcal m-2 y-1 P=1 R=2 AE=80% Carnivores A=8 E=7 I=10 P=10 R=50 AE=50% Herbivores A=50 E=40 I1=100 NPP=1000 R+E=1000 Plants A (GPP)=2000 AE= % Solar Energy= 1,000,000

Transfer Efficiencies Kcal m-2 y-1 P=1 I=10 R=2 AE=80% Carnivores A=8 E=7 P=10 R=50 I1=100 AE=50% Herbivores A=50 E=40 NPP=1000 R+E=1000 Plants A (GPP)=2000 AE= % Solar Energy= 1,000,000

Transfer Efficiencies Kcal m-2 y-1 P=1 I=10 R=2 AE=80% Carnivores A=8 E=7 P=10 R=50 I1=100 AE=50% Herbivores A=50 E=40 NPP=1000 R+E=1000 Plants A (GPP)=2000 AE=2% Solar Energy= 1,000,000

Transfer Efficiencies Kcal m-2 y-1 P=1 I=10 R=2 AE=80% Carnivores A=8 E=7 P=10 R=50 I=100 AE= % Herbivores A=50 E=40 NPP=1000 R+E=1000 Plants A (GPP)=2000 AE=2% Solar Energy= 1,000,000

Transfer Efficiencies Kcal m-2 y-1 P=1 I=10 R=2 AE=80% Carnivores A=8 E=7 P=10 R=50 AE=50% Herbivores A=50 E=40 I1=100 NPP=1000 R+E=1000 Plants A (GPP)=2000 AE=2% Solar Energy= 1,000,000

Transfer Efficiencies Kcal m-2 y-1 P=1 I=10 R=2 AE=80% Carnivores A=8 E=7 P=10 R=50 AE=50% Herbivores A=50 E=40 I=100 NPP=1000 R+E=1000 Plants A (GPP)=2000 AE=2% Solar Energy= 1,000,000

Transfer Efficiencies Kcal m-2 y-1 P=1 I=10 R=2 AE= % Carnivores A=8 E=7 P=10 R=50 AE=50% Herbivores A=50 E=40 I1=100 NPP=1000 R+E=1000 Plants A (GPP)=2000 AE=2% Solar Energy= 1,000,000

Transfer Efficiencies Kcal m-2 y-1 P=1 R=2 AE=80% Carnivores A=8 E=7 I=10 P=10 R=50 AE=50% Herbivores A=50 E=40 I1=100 NPP=1000 R+E=1000 Plants A (GPP)=2000 AE=2% Solar Energy= 1,000,000

Transfer Efficiencies Kcal m-2 y-1 P=1 I=10 R=2 AE=80% Carnivores A=8 E=7 P=10 R=50 AE=50% Herbivores A=50 E=40 I1=100 NPP=1000 R+E=1000 Plants A (GPP)=2000 AE=2% Solar Energy= 1,000,000

Transfer Efficiencies Kcal m-2 y-1 P=1 R=2 AE=80% Carnivores A=8 E=7 I=10 P=10 R=50 AE=50% Herbivores A=50 E=40 I1=100 NPP=1000 R+E=1000 Plants A (GPP)=2000 AE=2% Solar Energy= 1,000,000

Take home: Ecosystems are Energy Transformers Approximate 10% energy transfer between each trophic level More efficient energy use as you increase trophic levels Is there room for anyone else at the top of the pyramid? Which level is most important to pyramid stability?

Ray Lindeman 1942 First Ecosystem model

Eugene Odum 1953. Silver Springs, Florida.

Carbon cycle http://www.grida.no/climate/vital/13.htm, 1980-1989

Steady State (Equilibrium) Trillions of moles (per year) Turnover Time = 38,000,000/8400 = 4524 years Turnover rate is about 0.022% per year

ECOLOGICAL STOICHIOMETRY Elemental Ratios REDFIELD RATIO C:N:P 106:16:1 C:N – decaying wood, DOC. N:P -- cyanobacteria advantage. C:P – phosphate limitation for Daphnia.

ECOSYSTEM ECOLOGY ENERGY FLOW CHEMICAL CYCLES

Trophic Structure Principles Eltonian pyramids Number of individuals per species Is this pyramid stable?

Trophic Structure Principles What if we transformed each species into biomass instead of absolute numbers?

Trophic Structure Reminder Do biomass or counts include generation time/reproduction, how much energy is available for growth, or decomposers?

Measuring the Energy Content of Plants Calorimetry Heat generation Harvesting Linear growth Clip plots: why measure dry weight? CO2 uptake method Li-Cor photosynthesis system O2 output Lt. and dk. bottles Chlorophyll concentration Energy content measured using dry biomass b/c bulk of living matter in most species is water (fluctuates widely). About 95% dry weight made up of C compounds=equivalent to examining C compounds.

ECOSYSTEM SCALES

Ecosystem: (trophic-dynamic) the system composed of physical-chemical-biological processes active within a space-time unit of any magnitude… Ray Lindeman 1941 Cedar Ck. Bog, MN

Lake Wingra – ECOSYSTEM BOUNDARIES

ECOSYSTEM Compartments include leaves, wood, soil, rhizosphere. Small size scale. Compartments contain living & non-living

TROPHIC STRUCTURE Defined by energy flow. primary producer primary consumer (herbivore) secondary consumer (carnivore) …, top carnivore.  

BOUNDARIES

Average Annual Net Primary Productivity, by Habitat Ricklefs Fig. 6.8

Fig. 6.2 Ricklefs -- E.P Odum’s universal model of ecological energy flow

TROPHIC STRUCTURE Defined by energy flow. primary producer primary consumer (herbivore) secondary consumer (carnivore) …, top carnivore.  

Measuring Primary Productivity  Oxygen method c14 method – a radioactive tracer technique  annual production

CALORIMETRY Measuring Energy Flow calorie = 1 degree C increase at 15 degrees C, for 1 ml water 1000 calories = 1 Calorie carbohydrate and protein about 5 Cal per gram fat about 9 Cal per gram teaspoon sugar = 4 grams or 20 Calories (kilocalories)

TROPHIC CONCEPTS Productivity Biomass Turnover Time = Pool/Input = Biomass/Productivity Turnover Rate = Inverse of Turnover Time At equilibrium, Input = Output

ECOLOGICAL EFFICIENCY Ratio of the productivity for two adjacent trophic levels. EXAMPLE primary productivity = 2 grams per m2 per day herbivore productivity = 0.2 grams per m2 per day, then the ecological efficiency is: ???

Rule of Thumb The ecological efficiency is ~ 10% per trophic level.

TROPHIC CASCADES (CARPENTER) DIRECT & INDIRECT EFFECTS OF TOP PREDATORS ON BIOMASS PRODUCTIVITY

Bottom-Up; Top-Down effects

Microbial Loop Extra links reduce amount of energy reaching predators by about 90%.

Ammonium, Urea, Uric Acid Nitrogen Excretion: Ammonium, Urea, Uric Acid

Atmospheric Carbon & Global Warming

MASS BALANCE: Application of conservation of matter; Input & Output: Pool (Reservoir) Equilibrium Steady State Source & Sink Flux Net Turnover Rate & Time Burial Ricklefs Fig. 7.5 – Global Carbon Cycle

ECOSYSTEM MANIPULATIONS & THE NITROGEN CYCLE Bormann and Likens (1970) -- HUBBARD BROOK, NH ecological consequences of clear-cutting a 38‑acre watershed in a New Hampshire Experimental Forest Organic N oxidized to nitrate, producing nitric acid pH of stream decreased nitrogen fixation decreased nutrients rapidly flushed out of the watershed

[P04]: surrogate for primary productivity

PHOTOSYNTHESIS RESPIRATION

NPP = GPP - R Gross Primary Productivity Respiration Net Primary Productivity NPP = GPP - R