From ecosystem processes
to material and energy flows
– a perspective
• Samuli Launiainen
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Luonnonvarakeskus
Environment and processes interact via flows
Functional agents
• Plant individuals, species
• Forest floor, mosses, litter
• Soil layers
Physical environment
• Light, T, CO2, O3, pollutants
• Precipitation, soil water flows
Processes
Flows
• Physical, physiological, biological
– e.g. Photosynthesis, respiration
– Transpiration, evaporation, root uptake
• Create flows (fluxes) of C, H2O, energy
F = −k
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∂s
∂x
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Water, carbon and energy cycles coupled
Bonan, 2008 Science.
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Complex?
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APES – Atmosphere-Plant Exchange Simulator
A multi-species, multi-layer soil-vegetation-atmosphere transfer
model (Launiainen et al., 2015, in review)
Elementary scale: a horizontally homogenous canopy or soil layer
Upscaling from ’element scale’ processes to stand scale exchange
Backbones: biophysical theory, conservation of mass and energy
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APES – Atmosphere-Plant Exchange Simulator
Prosess-based, object-oriented – objects are instances of classes
• PlantTypes – vascular plants
• BryophyteTypes – mosses, lichens
• SoilProfile – soil domain
• Bedrock – below soil profile; mainly for boundary condition
• Stand – consists on PlantTypes, BryophyteTypes, SoilProfile
Classes contain
• Properties - physical, structural, physiological
• Functions/methods – ”processes specific to respective ecosystem
compartment”
• State variables – e.g. T, water content, LAI, stage of development,…
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PlantType -class
Leaf gas exchange, leaf temperature,
root uptake
• Vascular plant species, age cohorts etc.
• Structural properties
– LAI, WAI, PAI and their vertical profiles
– Fine root area, vertical profile
• Physical properties
– Leaf/needle dimension (for boundary layer cond.)
– Water storage capacity (interception, mm/LAI)
– (Optical properties)
• Ecophysiology
– Photosynthesis (Farquhar-model),f(TL, ΨL, z)
– Stomatal control (Medlyn et al. 2011), f(ΨL)
– Seasonal cycle (”S”)
• Phenology
Feedbacks
– LAI –dynamics (”DDsum”)
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Example: SoilProfile -class
Soil layers, horizons
• Water flow & conservation of
mass; Richard’s eq.
ψs(z), θ(z)
•
Heat flow & conservation of
energy; Fourier eq.
Ts (z)
Soil respiration Rs=f(Ts, θ)
Soil state variables
•
•
SoilProfile object
• Parameters ”soil type specific”
• Measurements / literature (pFcurves, Sat. Hydr. Cond.,
thermal conductivity
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Objects linked by
• Transport phenomena
– Micrometeorologic sub-models
• Feedbacks
– e.g. soil water status impacts leaf functioning; microclimate
affects leaf processes; leaf fluxes affect microclimate…
Modular
• Classes & sub-processes are mostly independent
• Structure is modular – easy to modify, extend and use
components in other models
Biophysical theory; classes are ’generic’
• Parameters can be measured or independently estimated.
• Easy (?) to apply for different type of ecosystems
In Matlab, partly Python
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Timescale ½ h: SW [Par,Nir (direct/diffuse)], LWdn, ea, Ta,Ca,Prec,U, (u*)
Site parameterization
Upper boundary conditions (meteorology)
Radiation
Air flow
Scalar transport
•
•
•
Qp(z),Qn(z),Rn*(z)
Canopy
Reynolds’stress,
U(z), Km(z)
h, LAI, Λl, Λr
Physiology
Phenology
BryophyteTypes (mosses)
Ta(z), ca(z), ea(z)
Iteration I
Iteration II: canopy water budget;
interception & wet leaf energy balance
momentum
Sink/source &
profiles
PlantTypes
•
•
•
Forest-atm flows
Iteration II: dry leaf energy
balance & gas exchange
Iteration II: moss energy &
water balance, gas exchange
SoilProfile
•
•
Physical properties (heat and water
balance)
Soil respiration
Iteration III: soil water and heat balance,
Soil respiration
Lower boundary conditions (at bottom of SoilProfile)
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CO2
H2O
Heat
Examples
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Heat, H2O and CO2 sinks/sources
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ecosystem scale flows
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Model
Hyytiälä SMEAR II: stand NEE May-Sept 2005
½ h flux
Measured
Source
Sink
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”Thinning”
Pine: LAI 3.0
2.0 m2m-2
Understory:
LAI 0.3
0.1 m2m-2
Field layer:
LAI 0.7 m2m-2
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Thinning impact on GPP
Total GPP May-Sept
•
•
•
drought
THINNED
• Removal of 33% of pine LAI
-24% GPP
• …but +15% if scaled per unit
remaining pine LAI
• … + ~25% if scaled per nr. trees
remaining
• Observations: increase in
annual volume growth >= 20%
during first 5 yr after thinning
Light competition
Water resources
Fertilization effect not
considered
UN-THINNED
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Kalevansuo, ground water level
•
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Horizontal flow to ditches: Hooghoud
drainage equation
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[email protected]
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