Using a global flux network fluxnet to study the breathing of the terrestrial biosphere
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Using a Global Flux Network—FLUXNET— to Study the Breathing of the Terrestrial Biosphere. Dennis Baldocchi ESPM/Ecosystem Science Div. University of California, Berkeley Collaborators

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Using a Global Flux Network—FLUXNET— to Study the Breathing of the Terrestrial Biosphere

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Using a Global Flux Network—FLUXNET— to Study the Breathing of the Terrestrial Biosphere

Dennis Baldocchi

ESPM/Ecosystem Science Div.

University of California, Berkeley


Rodrigo Vargas, Youngryel Ryu, Markus Reichstein, Dario Papale, Andrew Richardson, Deb Agarwal Catharine van Ingen, Bob Cook and Regional Networks


Melbourne, Australia


  • Network Background

  • Statistical Representativeness

    • Global Statistics on NEE, GPP, Reco

    • Network Size

    • Is the Statistical Distribution of Carbon Fluxes Invariant at the Global Scale?

  • Emergent Processes

    • Coupling between Photosynthesis and Respiration

    • PhotoDegradation, a New Process to Consider

    • Fluxes and Phenology

  • Space

    • Regional Flux Maps

    • Phenology Greenwave

Network of Regional Flux Networks

FLUXNET: From Sea to Shining Sea500+ Sites, circa 2009

Eddy Covariance Technique

  • Direct

  • In situ

  • Quasi-Continuous

  • Extended Footprint


  • Web sites



  • QA/QC

    • Data Standardization (names, units)

    • Version Control

  • Derived Flux Quantities

    • Gap-Filling

    • U* corrections for periods of low turbulence

    • Daily, Monthly, Annual Integrals

  • Flux Partitioning

    • Converting NEE into GPP and Reco

  • Compiling Multifaceted Site MetaData

  • Data Distribution

    • Search/Manipulate/Archive

Standard Processing Procedure

Vs non-standard, but Expert Based

Results and Discussion

Over-Arching Questions relating to Statistical Representativeness

  • As the sparse Network has grown, can it provide a Statistically-Representative sample of NEE, GPP and Reco to infer Global Behavior?, e.g. Polls sample only a small fraction of the population to generate political opinion

  • If mean Solar inputs and Climate conditions are invariant, on an annual and global basis,are NEE, GPP and Reco constant, too?; e.g. global GPP scales with solar radiation which is constant

  • Can Processes derived from a Sparse-Network be Upscaled with Remote Sensing and Climate Maps?; e.g. We don’t need to be everywhere all the time; We can use Bayes Theorem and climate records to upscale.

Global distribution of Flux Towers Covers Climate Space Well

Can we Integrate Fluxes across Climate Space,

Rather than Cartesian Space?

Apply Bayes Theorem to FLUXNET?

p(flux) from FLUXNET

p(climate|flux) prior from FLUXNET

p(climate) from climate database

Estimate Global flux by Integrating p(Flux|climate) across

Globally-gridded Climate space

Probability Distribution of Published NEE Measurements, Integrated Annually

Baldocchi, Austral J Botany, 2008

Updated PDF with 164 extra site-years

yields an insignificant change in the mean (P= 0.68)

Upscaling Flux Data with Remote Sensing Data

Published, Global: -182 gC m-2 y-1

Map, US: -189 gC m-2 y-1

Xiao and Baldocchi, unpublished

How many Towers are needed to estimate mean NEE,

And assess Interannual Variability, at the Global Scale?

We Need about 75 towers to produce robust Statistics

Little Change in Abiotic Drivers--annual Rg, ppt --across Network

Interannual Variability in NEE is small (between -220 to -243 gC m-2 y-1)

across the Global Network

Interannual Variability in GPP is small, too,

across the Global Network (1103 to 1162 gC m-2 y-1)

Potential and Real Rates of Gross Carbon Uptake by Vegetation:

Most Locations Never Reach Upper Potential

GPP at 2% efficiency and 365 day Growing Season


GPP at 2% efficiency and 182.5 day Growing Season

FLUXNET 2007 Database

Does Net Ecosystem Carbon Exchange Scale with Photosynthesis?

Ecosystems with greatest GPP don’t necessarily experience greatest NEE

Baldocchi, Austral J Botany, 2008

Ecosystem Respiration Scales Tightly with Ecosystem Photosynthesis,

But Is with Offset by Disturbance

Baldocchi, Austral J Botany, 2008

Decadal Plus Time Series of NEE:Flux version of the Keeling’s Mauna Loa Graph

Data of Wofsy, Munger, Goulden, et al.

Interannual Variation and Long Term Trends

in Net Ecosystem Carbon Exchange (FN), Photosynthesis (FA) and Respiration (FR)

Urbanski et al 2007 JGR

Interannual Variations in Photosynthesis and Respiration are Coupled

Baldocchi, Austral J Botany, 2008

What Happens to the Grass?



PhotoDegradation is a New and Emerging Process Affecting C Cycle in Semi-arid Grasslands

Baldocchi and Ma, unpublished

PhotoDegradation: A Process Not in Coupled Carbon-Climate Models

Baldocchi, Ma, Rutledge, unpublished

More Carbon is Lost with Rain Pulse on Dry Matter that has Been PhotoDegraded than Dry Matter in the Shade

Xu, Baldocchi, Tang, 2004

Global Biogeochem Cycles


Seasonality in GPP follows NDVI and Defines Growing Season

Ryu et al. in prep

Net Ecosystem Carbon Exchange Scales with Length of Growing Season

Baldocchi, Austral J Botany, 2008

Soil Temperature:

An Objective Indicator of Phenology??

Data of Pilegaard et al.

Soil Temperature:

An Objective Measure of Phenology, part 2

Baldocchi et al. Int J. Biomet, 2005

Spatialize Phenology with Transformation Using Climate Map

Baldocchi, unpublished

Flux Based Phenology Patterns with Match well with data from Phenology Network

White, Baldocchi and Schwartz, unpublished

Spatial Variations in C Fluxes with Remote Sensing

Do Snap-Shot C Fluxes, inferred from Remote Sensing, Relate to Daily C Flux Integrals?

Sims et al 2005 AgForMet

Spatial Variations in C Fluxes





Xiao et al. 2008, AgForMet


  • A sparse Global Network of Flux Towers produces statistically robust findings that are representative of broad climate and ecological zones that may integrated to validate models at grid/landscape/regional scales

  • Any Statistical Scaling Approach based on Climate must consider Disturbance and Stand Age, too.

  • A global Network of Flux Towers is discovering a number of emergent scale processes relating to the controls in inter-annual variability, controls by light, and phenology


  • NSF, Research Coordinated Networks

  • Microsoft, Regional Networks, ILEAPS

  • World-wide Collection of Collaborators and Colleagues, Technicians, Postdocs and Students

ANOVA analysis of the annual sums

A. Richardson & D. Baldocchi, unpublished

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