Two Years of Modelling

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Two Years of Modelling Tree-Ring Processes and
Stable Isotope Fractionations I.
Introduction to process modelling II. TreeRing
model III. Stable Isotopes in TreeRing Why
? Some theory - again Results IV. Future
work V. The Mystery Model - exclusive
unveiling
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A model is a generalised, hypothetical
description often based on an analogy, used in
analysing or explaining something Statistical
/ empirical black box approach, based on
applied relationships Theoretical /
physical based on physical principles Process u
sually involves interaction of various models
over time
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Schematic of TreeRing model
Pinus ponderosa tree ring image
LEAVES
EW
Photosynthate
False LW
Cambial model of cell division and growth
STEM
Available Carbon in stem
ROOTS
LW
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Location of ponderosa pine trees used for model
verification
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Response of some model parameters to climate
1985 - 1990
Degrees C
mm
V water / V soil
kg / m2 / h
MmCO2 / m3
1985
1986
1988
1987
1990
1989
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Modeled actual ring widths 1940 - 1995
Ring width (mm)
r 0.66
Year
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Modeled actual tree ring statistics 1940 - 1995
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What stable isotopes can add to the model

• Look in more detail at tree ring formation
  processes
• - Use of stored or present carbohydrates
• - Indicate gas exchange processes
• - Indicate timing of formation

• Verify model accuracy
• - Compare modelled with real isotopic time
  series
• - A check using isotopic theory

• Compare ring growth and isotope processes
• - Better understanding of ring development

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Schematic of TreeRing model with isotopes
Allocation and redistribution of ...
Transpiration
Pinus ponderosa tree ring image
Photosynthesis
CO2
Sucrose (used)
Starch (stored)
H2O
LEAVES
EW
CO2
Photosynthate
False LW
Cambial model of cell division and growth
STEM
Photosynthate
CO2
Photosynthate
ROOTS
LW
Water absorption
H2O
CO2
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20th century change in the d13C composition and
concentration of atmospheric CO2
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CO2 and H2O exchanges between leaf and atmosphere
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Basic model of C3 plant d13C composition
d13C composition of photosynthate and
atmospheric CO2
maximum diffusive fractionation (-4.4) and
maximum carboxylation fractionation (-29)
internal and atmospheric CO2 concentration
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Bucket model of soil water d18O dD
dD
d18O
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Actual precipitation d18O (1985) modeled soil
water d18O
d18O ()
Day in year
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Schematic of d18O and dD model
Roden et al., 2000
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Model of d18O and dD fractionation in leaf water
d1H or d16O ratio of leaf water, xylem water
and atmospheric water vapour
fractionation factors for liquid-vapour
(equilibrium), kinetic diffusion in air,
kinetic diffusion through boundary layer
vapour pressures of intercellular leaf air
spaces, boundary-layer, bulk air
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Modelled (a) and actual (b) whole leaf d13C
compositions for a single growth season
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Modeled actual tree ring d13C 1950 - 1995 each
ring is split into 3 sections, Pre1, Pre2, Post
d13C ()
d13C ()
Year
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Modeled tree ring d13C 1950 - 1995 atmospheric
d13C composition constant at -6.5
d13C ()
Year
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Modeled actual tree ring d13C 1950 -
1995 modeled using stored carbohydrates only
d13C ()
Year
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Modelled and actual cell d13C maintenance
respiration after growth
1982
1980
1981
1984
1983
1985
1986
1987
1988
1989
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Modeled actual tree ring d18O 1950 - 1995
d18O ()
Year
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Future Work NSF Grant Application to Coupled
Biogeochemical Cycles - Biocomplexity Modeling
whole tree responses to climate , enhanced CO2
and N Utilising the results from a 6-year
experiment at Placerville, California where
ponderosa pine were grown in ambient and enhanced
CO2 and N conditions. Will also involve measuring
isotopes in the collected samples. Biosphere-atm
osphere Interactions and Exchanges - Weizmann
Institute, Israel CarboEuroFlux - over 33 flux
towers across Europe The overarching goal of
CARBOEUROFLUX programme is to improve our
understanding on magnitude, location, temporal
behaviour and causes of the carbon source/sink
strengths of terrestrial ecosystems which can be
used to improve the negotiation capacity of the
European Community in the context of the Kyoto
protocol. Linked with EuroSiberianCarbonFlux,
OzFlux, JapanNet, AmeriFlux, AmazonFlux (LBA
CarbonSink), FLUXNET. Biosphere 2 - Rainforest
experiments of fluxes
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