Integrating Fluxes of Carbon Dioxide and Water Vapor

Integrating Fluxes of Carbon Dioxide and Water Vapor From Leaf to Canopy Scales Dennis Baldocchi Ecosystem Science Division/ESPM UC Berkeley

Outline • Overview Leaf-Canopy Scaling and Integration Concepts • Show Tests of Such Models over Multiple Time Scales • Use the CANVEG Model to Ask Ecophysiological and Micrometeorological Questions Relating to Trace Gas Fluxes

Classes of Model Complexity • The breadth and linkage of functional components that describe the biophysics of trace gas exchange. • How driving variables are defined and used as inputs to non-linear model algorithms. • The geometric abstraction of the canopy.

System Complexity: Interconnection of Key Ecosystem Processes ESPM 111 Ecosystem Ecology

Processes and Linkages: Roles of Time and Space Scales

3 -d Representation of Canopy Qi Chen and D. Baldocchi ESPM 111 Ecosystem Ecology

Geometrical Abstraction of the Canopy • One-Dimensional – Big-Leaf – Dual Source, Sun-Shade – 2 -Layer • Vegetation and soil – Multi-Layered • Two-Dimensional – Dual source • sunlit and shaded • Vegetated vs Bare Soil • Three-Dimensional – Individual Plants and Trees ESPM 111 Ecosystem Ecology After Hanson et al Ecol Appl 2004

Big-Leaf Model

2 -Layer/Dual Source Models

Dual Source Model: Discrete Form Whole Canopy

Role of Proper Model Abstraction ESPM 111 Ecosystem Ecology

Sunlit Leaf Area and Sun Angle

Multi-Layer Models

CANOAK Schematic

Basics of Ecosystem Models ESPM 111 Ecosystem Ecology

Quantifying Sources and Sinks • Biology: a(z), Ci, rs • Physics: rb, C(z)

Weight Source/Sink by Fraction of Sunlit and Shaded Leaves and Their Environment

Random Spatial Distribution: Poisson Prob Distr. Prob of Beam Penetration Prob of Sunlit Leaf

Sources of Spatial Heterogeneity • Vertical Variations in: – Leaf area index – Leaf inclination angles – Leaf Clumping – Leaf N + photosynthetic capacity – Stomatal conductance – Light, Temperature, Wind, Humidity, CO 2

Vertical Profiles in Leaf Area

Vertical Variation in Sunlight

Carboxylation Velocity Profiles

Profiles of Ci/Ca

Turbulence Closure Schemes • Lagrangian • Eulerian – Zero Order, c(z)=constant – First Order, F=K dc/dz – Second Order and ++ (dc/dt, dw’c’/dt)

Higher Order Closure Equations and Unknowns ESPM 228 Adv Topics Micromet & Biomet

Lagrangian Near- and Far-Field Theory ESPM 228 Adv Topics Micromet & Biomet

Dispersion Matrix ESPM 228 Adv. Topics Micromet & Biomet

Turbulent Mixing

Vertical Gradients in CO 2

Vertical Gradients in q and T

13 C Profiles

CANOAK MODEL Physiology Photosynthesis Stomatal Conductance Transpiration Micrometeorology Leaf/Soil Energy Balance Radiative Transfer Lagrangian Turbulent Transfer

Examples: Non-Linear Biophysical Processes Photosynthesis Transpiration Respiration Leaf Temperature

Why Non-linearity is Important?

Leaf Energy Balance • R: is shortwave solar energy, W m-2 • L: is Longwave, terrestrial energy, W m-2 • l. E: Latent Heat Flux Density, W m-2 • H: Sensible Heat Flux Density, W m-2 ESPM 129 Biometeorology 35

Leaf Energy Balance, Wet, Transpiring Leaf Net Radiation is balanced by the sum of Sensible and Latent Heat exchange ESPM 129 Biometeorology 36

Derivation 1: Leaf Energy Balance 2: Resistance Equations for H and l. E 3: Linearize T 4 and es(T) ESPM 129 Biometeorology 37

Linearize with 1 st order Taylor’s Expansion Series ESPM 129 Biometeorology 38

Linearize the Saturation Vapor Pressure function ESPM 129 Biometeorology 39

• Wc, the rate of carboxylation when ribulose bisphosphate (Ru. BP) is saturated • • Wj, the carboxylation rate when Ru. BP regeneration is limited by electron transport. • Wp carboxylation rate with triose phosphate utilization ESPM 228, Advanced Topics in Micromet and Biomet

If Wc is minimal, then: If Wj is minimal, then If Wp is minimal, then ESPM 228, Advanced Topics in Micromet and Biomet

Analytical Equation for Leaf Photosynthesis Baldocchi 1994 Tree Physiology ESPM 228, Advanced Topics in Micromet and Biomet

Seasonality in Vcmax Wilson et al. 2001 Tree Physiol ESPM 228, Advanced Topics in Micromet and Biomet

Results and Discussion

Model Test: Hourly to Annual Time Scale

Model Test: Hourly Data

Time Scales of Interannual Variability

Spectra of Photosynthesis and Respiration

Model Test: Daily Integration

Interannual Variability

Model Validation: Who is Right and Wrong, and Why? How Good is Good Enough? Hansen et al, 2004 Ecol Monograph ESPM 111 Ecosystem Ecology

Decadal Power Spectrum of CO 2 and Water Vapor Fluxes

NEE and Growing Season Length

GPP

Component C Fluxes

Light Use Efficiency and Net Primary Productivity NPP=e f Qp

LUE and Leaf Area

LUE and Ps Capacity

Emergent Processes: Impact of Leaf Clumping on Canopy Light Response Curves

Role of Leaf Clumping on Annual C and H 2 O Fluxes

Interaction between Clumping and Leaf Area

How Sky Conditions Affect NEE?

Knohl and Baldocchi, JGR Biogeosci 2008

Knohl and Baldocchi, 2008 JGR Biogeosci

Potential Impact of Aerosols/Clouds on NEE

Oxygen and NEE: Paleoclimates

Do We Need to Consider Canopy Microclimate [C] Feedbacks on Fluxes?

Leaf Temperature and Isoprene Emission?

Leaf size, CO 2 and Temperature: why oak leaves are small in CA and large in TN

Physiological Capacity and Leaf Temperature: Why Low Capacity Leaves Can’t Be Sunlit: : or don’t leave the potted Laurel Tree in the Sun

Below Canopy Fluxes

Below Canopy Fluxes and Canopy Structure and Function

Impact of Thermal Stratification

Impact of Litter

Conclusions • Biophysical Models that Couple Aspects of Micrometeorology, Ecophysiology and Biogeochemistry Produce Accurate and Constrained Fluxes of C and Energy, across Multiple Time Scales • Models can be used to Interpret Field Data – LUE is affected by LAI, Clumping, direct/diffuse radiation, Ps capacity – NEE is affected by length of growing season – Interactions between leaf size, Ps capacity and position help leaves avoid lethal temperatures – Below canopy fluxes are affected by T stratification and litter