Carbon Cycle at Global, Ecosystem and Regional Scales Dennis
Baldocchi University of California, Berkeley Bev Law Oregon State
University, Corvallis
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Topics Concepts Stores, pools, fluxes, processes Carbon Stores
and Fluxes Stores: Vegetation and Soil C = f(x,y,z) Fluxes: NEP =
f(x,y,t) Global Fluxes Regional Fluxes (WA, OR, CA)
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How Does Contemporary Carbon Cycle Differ from Pre- Settlement
Times? What types of landscapes are better or worse sinks for
Carbon? How does Carbon Assimilation and Respiration respond to
Environmental stresses, like drought, heatspells, pollution? Are
Forests Effective Mitigators for stalling Global Warming? Big
Questions
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Methods To Assess Terrestrial Carbon Budgets at Landscape to
Continental Scales, and Across Multiple Time Scales Global
Circulation Model Inversion Remote Sensing Eddy Flux Measurements/
Flux Networks Forest/Biomass Inventories Biogeochemical/ Ecosystem
Dynamics Modeling Physiological Measurements/ Manipulation Expts.
Ice Cores
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CO 2 => 280 ppm during Inter-Glacial, over 10k years CO 2
=> 180 ppm during Glaciation, over 100k years
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Dust, Life, Oceans, CO 2 and CH 4 Amplify Feedbacks on
Climate
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Contemporary CO 2 Record Sources: Fossil Fuel Combustion
Deforestation Cement Production Soil and Plant Respiration
Volcanoes Sinks: Photosynthesis, Land/Ocean C Burial in
Wetlands
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Global Carbon Cycle: Gross Fluxes and Pools
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Net Global Carbon Fluxes, 10 15 gC y -1
1970-19991990-19992000-2006 Fossil Fuel Emission + Cement 5.66.57.6
Land use Change 1.51.61.5 Atmospheric Uptake 3.13.24.1 Ocean uptake
2.02.2 Land Uptake 2.02.72.8 Canadell et al. 2007 PNAS
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Perspective How big is 1 Peta (10 15 ) gram? 1 Giga-ton (Gt)
Billion-Million grams Billion cars (@ 1 ton each) 1 10 15 gC/100 10
12 m -2 ~10g m -2 =10 cm 3 m -2 Equivalent to a 10 micron layer of
water over a meter-squared surface across the land 1g = 1 cm 3 1 m
3 = 10 6 g = 1 Mt Water Reservoir, 1 km 3 = 1Gt
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How much is C in the Air? Mass of Atmosphere F=Pressure x
Area=g x Mass Surface Area of the Globe = 4 R 2 M atmos = 101325 Pa
4 (6378 10 3 m) 2 /9.8 m 2 s -1 = 5.3 10 21 g air Compute C in
Atmosphere @ 380 ppm Pg/ppm
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CO 2 in 50 years with Business as Usual Current Anthropogenic C
Emissions 7 GtC/yr, (1 GtC = 10 15 g=1Pg) 45% retention in
Atmosphere Net Atmospheric Efflux over 50 years 7 * 50 * 0.45 = 157
GtC Atmospheric Burden over 50 years 833 (@380 ppm) + 157 = 990
GtC, Conversion back to mixing ratio 451 ppm ( 2.19 Pg/ppm) or 1.6
x pre-industrial level of 280 ppm To keep atmospheric CO 2 below
450 ppm the World must add less than157GtC into the atmosphere
PERIOD Natural Growth in Population and Economies has Anthropogenic
emissions slated to grow to 16 GtC/y by 2050.
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C Fluxes Across the World
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Schulze, 2006 Biogeosciences NBP NEP GPP NPP R h R a
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FLUXNET: From Sea to Shining Sea 500+ Sites, circa 2009
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Probability Distribution of Published NEE Measurements,
Integrated Annually
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Data of Wofsy et al; Urbanski et al. JGR 2008 Season Course in
Daily GPP and Reco for a temperate deciduous forest
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Odum, 1969, Science Conceptual Paradigm: Net Ecosystem
Productivity (P N ) is a function of age, in responses to changes
in Biomass (B), gross primary productivity (P G ) and respiration
(R) Years
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Urbanski et al. 2007, JGR C fluxes of a Middle-Age Temperate
Deciduous Forest Continue to change with Stand Age Re-growth after
1938 Hurricane
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Baldocchi, Austral J Botany, 2008 Ecosystem Respiration (F R )
Scales with Ecosystem Photosynthesis (F A ), But with an Offset by
Disturbance
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Baldocchi, Austral J Botany, 2008 Interannual Variations in
Photosynthesis and Respiration are Coupled
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Law and Ryan, 2005, Biogeochemistry C Cycling, Below
Ground
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Soil Respiration and Temperature, Adequate Soil Moisture Soil
Respiration and Declining Soil Moisture
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Impact of Rain Pulse and Metabolism on Ecosystem respiration:
Fast and Slow Responses Baldocchi et al, 2006, JGR
Biogeosciences
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Regional Carbon Budget Approach Washington, Oregon, California
Objectives: Reduce uncertainty in estimates Multiple modeling
approaches Multiple observation datasets Effects of disturbance and
climate on carbon balance (past 35 years)
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ORCA Top-Down Modeling Concept
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Diagnostic Carbon Flux Model (BioFlux)
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Oregon & California Carbon Budget (1996-2000 means) OR: C
sequestered as NBP + accum. in forest products = 50% ff CA: 10% of
equivalent fossil fuel emissions (NBP = NEP harvest fire; OR 17 -
10.7 0.4 = 5.9 TgC)
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Carbon Emission and Ecosystem Services US accounts for about
25% of Global C emissions 0.25*7.0 10 15 gC = 1.75 10 15 gC Per
Capita Emissions, US 1.75 10 15 gC/300 10 6 = 5.833 10 6 gC/person=
5.833 mtC Ecosystem Service, net C uptake ~100-200 gC m -2 Land
Area per Person 3.03 10 4 m 2 /person ~ 1.5- 3.0 ha/person US Land
Area 9.1 10 8 ha 8.75 10 8 to 1.75 10 9 ha needed by US population
to offset its C emissions Naturally!
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What is the Upper Bound of GPP? Bottom-Up: Counting
Productivity on leaves, plant by plant, species by species
Top-Down: Energy Transfer
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Upper-Bound on Global Gross Primary Productivity Global GPP is
~ 120 * 10 15 gC y -1 Solar Constant, S* (1366 W m -2 ) Ave across
disk of Earth S*/4 Transmission of sunlight through the atmosphere
(1-0.17=0.83) Conversion of shortwave to visible sunlight (0.5)
Conversion of visible light from energy to photon flux density in
moles of quanta (4.6/10 6 ) Mean photosynthetic photon flux
density, Q p Fraction of absorbed Q p (1-0.1=0.9) Photosynthetic
efficiency, a (0.02) Arable Land area (~ 110 * 10 12 m 2 ) Length
of daylight (12 hours * 60 minutes * 60 seconds = 43200 s/day)
Length of growing season (180 days) Gram of carbon per mole (12)
GPP = 1366*0.83*0.5*4.6*0.9*0.02*110 10 12 *43200*180*12/(4 10 6
)=120.4 * 10 15 gC y -1
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Gifford, 1994, Australian J Plant Physiol The Ratio between
Respiration and Photosynthesis is Constant: Regardless of Plant
Size, Treatment etc Emerging and Useful Ecological Rules
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Luyssaert et al. 2007, GCB GPP and Climate Drivers Climate
explains 70% of variation in GPP
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NEP and Climate Drivers Luyssaert et al. 2007, GCB Climate
explains 5% of variation in NEP