1. Ecosystem Energy and Nutrient Flow

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

3. Function, not Species -- Stuff, not Things

4. 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

5. ECOSYSTEM ECOLOGY
ENERGY

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

7. 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?

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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

22. 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?

23. Ray Lindeman 1942
First
Ecosystem model

24. Eugene Odum 1953.
Silver Springs, Florida.

25. Carbon cycle

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

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

31. ECOSYSTEM ECOLOGY
ENERGY FLOW
CHEMICAL CYCLES

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

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

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

35. 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.

36. ECOSYSTEM
SCALES

37. 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

38. Lake Wingra – ECOSYSTEM BOUNDARIES

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

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

41. BOUNDARIES

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

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

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

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

46. 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)

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

48. 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: ???

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

50. TROPHIC CASCADES (CARPENTER) DIRECT & INDIRECT EFFECTSOF
TOP PREDATORS ON
BIOMASS
PRODUCTIVITY

51. Bottom-Up; Top-Down effects

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

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

54. Atmospheric Carbon & Global Warming

55. 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

57. 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

58. [P04]: surrogate for primary productivity

59. PHOTOSYNTHESIS
RESPIRATION

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