espm 111 Energy - Rausser College of Natural Resources

2/11/2013

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ESPM 111 Ecosystem Ecology

ENERGY & ECOSYSYEM ECOLOGY

Dennis BaldocchiESPM

University of California, Berkeley

2/11/2013

Overview

• Concepts and Units of Work and Energy

• Solar Energy– How Much, When and Where

• Net Radiation Balance– shortwave and longwave energy

• Energy Partitioning– Sensible and Latent Heat Exchange

• Radiation Transfer through Vegetation


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‘Our bodies are stardust;Our lives are sunlight’

Oliver Morton, 2008 Eating the Sun: How Plants Power the Planet

ESPM 111 Ecosystem EcologyZhu et al. 2010 Ann Rev Plant Biol

Eating the Sun: Converting Solar Energy to Biomass on an Ideal Summer DayNot the Annual Efficiency

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• 8 Photons per CO2 molecule fixed

• 4 e- released with each water molecule that is split

• 496 kJ/mole CO2, Energetics of photosynthesis– 4 e- times 125 kJ mole e-

• 13%, Maximum Efficiency of sunlight to stored carbon

• 9%, Ideal photosynthetic efficiency– Considering photorespiration and leaf absorptance

• 2%, Typical Maximum Efficiency Observed in the field

• Potential Gross Primary Productivity using Annual Average Sunlight– 12 g/mole C * 0.02 mol C/mole quanta * Rg/2 *4.6 (mole quanta

m-2 )– 12 * 0.02 * 161/2 * 4.6e-6 * 12*3600*365=1401 gC m-2 y-1


Theoretical and Potential Photosynthetic Efficiencies

ESPM 111 Ecosystem EcologyBurgin et al 2011 Frontiers Ecology

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ENERGY = WORK

WORK = FORCE times DISTANCE (m)

ENERGY FLUX DENSITY (W m-2 =J m-2 s-1 = kg s-3 )

FORCE (kg m s-2) = MASS (kg) times ACCELERATION (m s-2)

UNITS: Joule = Newton-meter=N-m = kg m2 s-2

Power= Watt = J s-1

Power = dWork/dTime = dW/dt


First Law of Thermodynamics:

• The change in internal energy (U) is a function of the change in the amount of heat absorbed or lost (Q) and the change in amount of work done on the system (W)

– Energy cannot be created, nor destroyed; it can only be transferred from one state to another.

– The total amount of energy in a closed system is constant

– Life and Ecosystems are Open Systems

U U U Q W2 1

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Allen and Martin, 2007 Nature

Light (‘Hill’) Z Reactions:PS II and Ps I

680 nm

700 nm

• Light Energy (400 to 700 nm) is absorbed by pigments

• This energy splits water and releases 4 electrons, e-

• These Electrons produce biochemical energy compounds, ATP and NADPH

• Photosystem II uses 680 nm energy to generate ATP (non-cyclic electron transport)

• PS I uses 700 nm solar energy to generate NADPH (cyclic electron transport).

• 8 Photons per CO2 molecule are fixed

• Excess energy is lost as heat or fluorescence.

Solar Energy Produces Chemical Energy Used by Life


Energy from Redox, e.g. Microbial Battery

Reduction, Gain of Electrons (GER)Oxidant + e- ==> Product

Oxidation, Loss of Electrons, (LEO)Reductant ==> Product + e-

Oxidizing agent is Reduced and gains Electrons, so it is also the Electron Acceptor, e.g. O2 and SO4--

A Reducing agent is Oxidized and looses Electrons, so it is also the Electron Donor, e.g. (CH2O)n

OIL (Oxidation is Loss) RIG (Reduction is Gain)

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CH2O => C4+ + 4 e- + H2O

CarboHydrate is an electron donor

Aerobic Respiration of CarboHydrates Produce Energy for Life

Oxygen is an electron acceptor

O2 + 4e- + 4H+ => H2O + energy

Change in Gibbs free Energy, G = -125 kJ mole-1 e-


Nerst Equation

Computes Redox Cell Potential

0

[ ]ln

[ tan ]i

RT oxidantE E

nF reduc t

(voltage, or Electromotive Force)

G = (Ei-E0) n F

Gibbs Free Energy, G

n is charge numberF is Faraday constant, 96.84 kJ per volt gram equivalent

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Reductions Pe0

(Water@pH=7) = log(K)

Eh(mv) =RT ln K/nF

G = Eh nFkJ/e-

A ¼ O2 + H+ + e- = ½ H20 13.75 809 78B 1/5 NO3- + 6/5 H+ + e- = 1/10 N2 + 3/5

H2O12.65 744 72

CD 1/8NO3- + 5/4 H+ + e- = 1/8 NH4+ + 3/8

H2O6.15 362 35

EF ½ CH2O + H+ + e- = ½ CH3OH -3.01 -177 -17G 1/8 SO4

-- + 9/8 H+ + e- = 1/8 HS- + ½ H2O

-3.75 -221 -21

H 1/8 CO2 + H+ + e- = 1/8 CH4 + ¼ H2O -4.13 -243 -23J 1/6 N2 + 4/3 H+ + e- = 1/3 NH4

+ -4.68 -275 -26.7

Oxidation Pe0 (Water @ pH=7) = -log(K)

L ¼ CH2O + ¼ H2O = ¼ CO2 + H+ + e- -8.20 -482 -46.7L1 ½ HCOO- = ½ CO2 + ½ H+ + e- -8.73 -513 -49.7L2 ½ CH2O + ½ H2O = ½ HCOO- + 3/2 H+ +

e-

-7.68 -452 -43.8

L3L4 ½ CH4 + ½ H2O = ½ CH3OH + H+ + e- 2.88 169 16.4M 1/8 HS- + ½ H2O = 1/8 SO4

-- + 9/8 H+ + e-

-3.75 -221 -21.4

NO 1/8 NH4+ + 3/8 H2O => 1/8 NO-3 + 5/4 H+

+ e-6.15 -362 35

P

Derived from Strumm and Morgan

Redox Equations for Life

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E(red)-E(ox) G kJ e- eq-1 Energy, kJ

Aerobic respiration A + L -(78 - -47) -125 3000 kJ/mole C6H12O6

Denitrification B + L -(72 - -47) -119 2856 kJ/ mole C6H12O6

Nitrate reduction D + L -(35 - -47) -82

Fermentation F + L -(-17 - -47) -30 240 kJ/mole C6H12O6

Sulfate reduction G + L -(-21 - -47) -25

Methane fermentation H + L -(-23 - -47) -24 576 kJ/ mole C6H12O6

N fixation J + L -(-27 - -47) -20

Sulfide oxidation A + M -(78 - -21) -100

Nitrification A + O -(78 – 35) -43 344 kJ/mole NH4

+

Energy Yields from CarboHydrates


Solar Facts

• Solar Constant: 1366 W m-2

• Solar Radiative Temperature: 5770 K

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http://www.globalwarmingart.com/images/4/4c/Solar_Spectrum.png


Planck’s Law

k is the Boltzmann constant, 1.381 10-23 J molecule-1 K-1

h is Planck's constant, 6.626 10-34 J s

c is speed of light, 2.99972 * 108 m s-1

(m)

0.1 1

E(

,T)

0

2e+13

4e+13

6e+13

8e+13

1e+14

Tsun = 5770KFaint Sun (70% of contemporary), T=5213 K)1)(exp(

2),(

),(

5

2*

kThc

hcTE

d

TdE

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Distribution of Solar Energy by Waveband:Color is a function of the Black Body Temperature

Monteith and Unsworth

Waveband (nm) Energy %

0-300 1.2

300-400, ultra-violet 7.8 SUNBURN

400-700, visible/PAR 39.8 PHOTOSYNTHESIS

700-1500, near infrared

38.8 SUNSTROKE/OVERHEATING

1500 to infinity 12.4 Heat Emission


L TkA 4

LONGWAVE ENERGY EMISSION is a Function of Temperature to the 4th power

is the Stefan-Bolztmann constant, 5.67 10-8 W m-2 K-4.

4),( TLdTE

Area under the Curve of Planck’s Law

is emissivity, 0 to 1; for leaves

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(m)

0.1 1 10 100

E(

,T)

1e+3

1e+4

1e+5

1e+6

1e+7

1e+8

1e+9

1e+10

1e+11

1e+12

1e+13

1e+14

1e+15

T=5770 K

T=298 K

Solar shortwave energy

Terrestrial Longwave energy

WaveLength

Comparative Energy Spectra:Note Magnitude and Wavelength


Grassland 2001

Day

0 50 100 150 200 250 300 350

Ra

dia

tio

n F

lux

De

ns

ity

(MJ

m-2

d-1

)

0

10

20

30

40

Amount of Radiation Available to an Ecosystem, in California:Sets Upper Limit for Utilizing Biofuels for Energy

6474 MJ m-2 year-1

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The radiation normal to a surface is a function of the projection of area normal to incident rays on a flat surface:

Lambert’s Cosine Law

Zenith Angle

Elevation angle

FLUXNET database

Latitude

0 10 20 30 40 50 60 70 80 90

Rg

(MJ

m-2

y-1

)

0

2000

4000

6000

8000

Energy Drives Metabolism:How Much Energy is Available and Where

Solar Radiation Decreases with increaseing Latitude, except near the Tropics due to Clouds

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R R L Ln g B A( )1

R R L Tn g s B ( )1 4

• Net Radiation is comprised of the balance between incoming and outgoing Solar (shortwave) and Terrestrial (Longwave) Radiation


FLUXNET database

Latitude

0 10 20 30 40 50 60 70 80 90

Rn

(M

J m

-2 y

-1)

0

1000

2000

3000

4000

5000

Net Radiation Budgets across the Globe:Affected by Vegetation, Albedo, Surface and Air Temperature

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( ) ( ) ( ) 1

Absorption + Reflectance + Transmission = 1

What Happens to Photons Hitting a Leaf?

Transmittance

Reflectance

Incidence

Absorptance


Blue oak leaf

Wavelength, nm

500 1000 1500 2000 2500 3000

Re

flect

an

ce

0.0

0.2

0.4

0.6

0.8

Leaf Reflectance Spectrum, shortwave energy

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2/11/2013 ESPM 129 Biometeorology 29

Reflectance spectra of an annual grassland

Data collected by M. Falk, Ma, Baldocchi


Planetary ALBEDO

Earth ~ 30%

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GLOBAL ALBEDO


The Real ‘ALBEDO’

Wavelength (nm)

300 400 500 600 700 800 900 1000

Re

flect

ance

0.0

0.2

0.4

0.6

0.8

1.0

His Spectral Reflectance

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Vegetation Albedo differs with Canopy Structure

Orick, CA

Dark, Old Growth Redwoods and Brighter Logged and Regrowth Patches


Ogunjemiyo et al., 2005

Tall, Rough, Forests Trap more Sunlight:Douglas fir Forest, Pacific Northwest

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Albedo varies with canopy Nutrition

ESPM 111 Ecosystem EcologyOllinger et al. 2008 PNAS


Snow Reflectance Differs with the Presence and Absence of Trees

Notice the dark spots from the interception of light by the boreal forest, even though the landscape is covered with snow, a larger scale example of the one demonstrated in the previous figure

http://modland.nascom.nasa.gov/gallery/?JamesBay.A2000055.1645.1110x840.jpg

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R H E G S Pn s

• Net Radiation is partitioned into– Sensible Heat Exchange (H)

– Latent Heat Exchange (E)

– Soil Heat Exchange (G)

– Heat Storage in the Air and Vegetation (S)

– Photosynthesis (Ps)

Units: J m-2 s-1 = W m-2

Radiation Budget


BorealForest

PBL3000 m

PBL 1500 m

25 m

S = 0.03 R nG = 0.02 R n

S = 0.07 R nG = 0.03 Rn

10 m

LE = 0.65 R n

H = 0.3 R n

LE = 0.25 R n

H = 0.65 Rn = 0.10 R g Rn = 0.87 R g

= 0.10 R g Rn = 0.87 R g

Temperate Forest

Comparative Energy Fluxes

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Light transmission through a forest canopy

Sunlight passing through gaps comes from the sun and from the sky. Leaves intercept, absorb, reflect and transmit light. This causes complementary radiation

Pt. Reyes National Seashore, Allomere Falls trail, August 2002


Patterns of Sunflecks, Umbra and Penumbra

Gap Fraction, Probability of Beam Penetration, P0

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Sun Angles and the probability of beam penetration, P0

leaf area index

0 1 2 3 4 5 6

P0(L

)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

90o

30o

45o

600

spherical distribution, G=0.5

PLG LG

sun sun0 exp(

cos) exp(

sin)

L: Leaf area IndexG: direction cosine, leaf normal vs solar zenith angle

Beer’s Law

(-kL)=P0 exp


Probability of beam penetration with clumped and randomly distributed foliage

leaf area index

0 1 2 3 4 5 6

P0(L

)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

random distribution

clumped distribution

spherical distribution, G=0.5, =45o

)sin

G L(-exp=P0

, clumping coef

(-kL)=P0 exp

Beer’s Law

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Points To Ponder

• How much Energy is Available to a square meter of soil over a Year?

• How does this integrate over the area of the State or Nation?

• How does this number compare with the Energy we use to travel, heat our homes, produce our food and fiber and support our recreation?

• Change Land Use Change, with a change in Albedo, function as a way to offset Global Warming?


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How Does Energy Availability Compare with Energy Use?

• US Energy Use: 105 EJ/year– 1018J per EJ– 3.5 1011 J/capita/year

• US Land Area: 9.8 106 km2=9.8 1012 m2

• Energy Use per unit area: 1.07 107 J m-2

• Potential, Incident Solar Energy: 6.47 109 J m-2

– Ione, CA

• A solar system (solar panels, biomass) must be 0.1% efficient, working year round, over the entire surface area of the US is needed to capture the energy we use to offset fossil fuel consumption– Alternatively, a 1% efficient system, on 10% of the surface area,

will provide US Energy, assuming available water and not considering energy inputs to drive the system


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Ohm’s Law

Current = Volts/Resistance, I = V/R

Power = Current * Current * Resistance, I2 R

Power=dW/dt = Volts * Current, V * I

Gibbs Free Energy: G =- E’ n F (kJ mole-1);

E, voltage from Nerst Equ; n: charge; F: Faraday Const. 96 kJ per volt gram eq

Volts <<=>> Energy


m )

0.0 0 .5 1 .0 1 .5 2 .0 2 .5 3 .0

S(

) (

W m

-2

m-1

)

0

500

1000

1500

2000

2500

SOLAR ENERGY SPECTRUM

Extra-Terrestrial Spectrum

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RedoxPotential (mv)

Energy Release (J/mole e-)

Reduction of O2

812 125

Reduction of NO3-

747 118.9

Reduction of Mn4+ to Mn2+

526 97.4

Reduction of Fe3+ to Fe2+

-47 42.2

Reduction of SO42- to H2S

-221 24.6

Reduction of CO2 to CH4

-244 23.4

2 24 4 2O H e H O

3 2 22 2NO H e NO H O

2 4 28 8 2CO H e CH H O

Schlesinger, 1997

24 2 210 8 4SO H e H S H O

22 24 2 2MnO H e Mn H O

22( ) 3 3Fe OH H e Fe H O

Microbes prefer Hierarchy of Energy Yields

espm 111 Energy - Rausser College of Natural Resources

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